The conviction, the third of its kind involving Scientologists in France, was dismissed by the US-based church as "politically motivated" and "religious McCarthyism".
Xavier Delamare, former head of the church in the Marseille and Toulon area, was fined pounds 10,000 and given a two-year jail sentence, 18 months of which was suspended. Four other scientologists were convicted of similar offences and given suspended jail sentences. Two were cleared.
At their trial in September it was revealed that five boxes of sealed prosecution documents had been mysteriously destroyed. That was the third time legal documents in cases against scientologists had disappeared in France in three years, leading to claims that the sect had "penetrated" the French state. Later, the papers were said to have been shredded in error by a court clerk.
Mr Delamare and others were accused of cheating 10 people of sums ranging from pounds 2,400 to pounds 15,000 between 1987 and 1990. The prosecution said victims were tricked or morally blackmailed into buying "dianetic" and "mental science" courses to purify the mind and remove "undesirable sensations" at a cost of pounds 120 an hour.
The Church of Scientology, founded by the American science fiction writer L Ron Hubbard in 1954, claims to be able to rescue scientific knowledge from war-like purposes and use it for the moral and physical well-being of the human race. It is believed to have eight million disciples in the world and 10,000 in France.
The church said yesterday that Mr Delamare had broken the sect's own rules and been punished internally. The convictions were the result of an atmosphere of "religious McCarthyism" in France after an inter- ministerial committee "to fight against sects" had condemned Scientology earlier this year, it said.