Frederick W. Devine, who campaigned against corruption to become one of the state's most powerful construction union leaders in the early 1990's, was convicted yesterday in Manhattan on charges that he stole more than $50,000 from a fund earmarked to create jobs for unemployed carpenters.

He was found guilty by a jury of siphoning the money to pay for lavish winter vacations in Florida from 1993 to 1996 for himself, his wife, his relatives, a female companion and some of his friends. He was also convicted of using the fund to cover the cost of using a private jet twice to visit another female companion in Rochester.

The president of the 25,000-member District Council of Carpenters and Joiners in New York City and Vicinity from 1991 to 1996, Mr. Devine showed no emotion as the jury announced that it had found him guilty of six counts of grand larceny and acquitted him of two grand larceny counts and one count of conspiring to defraud the fund.

During his five years as the head of the nation's largest regional carpenters' union, Mr. Devine -- with a salary of $410,000 a year -- was courted by political candidates who sought his union's endorsement and financial support.

Mr. Devine, 58, faces a maximum prison term of 15 years. He was freed without bail, pending motions by his lawyers to overturn the conviction.

The verdict came after a three-week trial in State Supreme Court in Manhattan and was viewed by labor experts as a major triumph for prosecutors in the Manhattan District Attorney's office, who spent two years on the case.

''This is a significant victory against labor corruption,'' said James F. McNamara, the research director of the Association for Union Democracy, a group that monitors union activities. ''Without informing his members, Devine used their money to create a slush fund for his personal use and glorification.''

Paul A. Victor, Mr. Devine's chief lawyer, said he would ask the acting State Supreme Court Justice, Colleen McMahon, who presided at the trial, to set aside the guilty verdicts on the grounds of insufficient evidence and that there was no proof of criminal intent by Mr. Devine.

A grand jury indictment in 1996 accused Mr. Devine of misappropriating more than $200,000, but yesterday's verdicts left unclear how much the jury believed he had actually stolen. The jury found him guilty of one ''C'' felony count of grand larceny, which specifies a theft of more than $50,000. The five other guilty verdicts were for ''D'' felony counts, for thefts of amounts from $3,000 to $50,000 each.

Mr. Devine began working in a carpenters' local as a teen-ager, repairing and building docks and foundations for skyscrapers. Over the next 40 years, he battled for union posts saying he would extend democratic rights to rank-and-file members. In 1991, he ran for president of the District Council of Carpenters and Joiners, portraying himself as a reform candidate who would end corrupt practices in the union. He was elected, and then re-elected in 1995.

In June 1996, Mr. Devine was abruptly ousted from his posts by officials of the national carpenters' union who cited complaints by members of excessive spending and assertions by a court-appointed monitor that he had helped mobsters and their relatives get jobs at the Jacob K. Javits Convention Center.

The criminal accusations stemmed from expenditures that he authorized from 1993 to 1996 as the district council's president and as the administrator of a regional Labor-Management Cooperation Trust Fund that was established to create union jobs in the city, the northern suburbs and on Long Island.

Michael Bixon, the lead prosecutor, cited the testimony of witnesses and a paper trail of financial records to argue that Mr. Devine's authorized improper payments for himself and others for hotel suites in Fort Lauderdale, Fla., limousine rentals, massages, beauty parlor visits and golf parties. Mr. Bixon said that Mr. Devine spent about $9,000 for two private plane trips in 1993 and in 1994 to Rochester to visit a female union official with whom he was having a romantic relationship.

Mr. Victor, the defense lawyer, contended that Mr. Devine and his associates went to Florida for annual conferences with other union officials. Mr. Victor said that Raymond O'Kane, a former top aide to Mr. Devine, was responsible for the misappropriations. Questioning Mr. O'Kane's credibility as the prosecution's star witness, Mr. Victor said that Mr. O'Kane brokered a lenient plea deal with prosecutors in 1996 after learning that he was being investigated for misusing union funds.

Mr. Victor, in his closing argument, said Mr. Devine's trips to Rochester were for legitimate purposes, not for romantic trysts.

''Prosecutors should stay out of the bedrooms and not prosecute sin,'' Mr. Victor told the jury. ''That's God's jurisdiction.''