The woman succeeded in getting around 400 million yen out of the man over a seven-year period, in what he said he thought were loans, which she used to buy luxury cars and a condominium, the Sports Nippon newspaper said.
"She had no ability nor any intention to repay the debts," said the court in Shizuoka, central Japan, according to the paper yesterday.
The court heard how the woman, who was not named, used what it called an "amorous net" to persuade him to part with the cash, including stripping naked in hotel rooms and asking him to bathe her.
The elderly couple began dating in June 2000, the paper said, and the woman repeatedly asked for money, which she said was to pay off debts to another man whom she would otherwise have to marry.
The man, whose identity was also not revealed, sold land he had inherited and took out loans to meet her demands.
She used the money to buy top-end cars, including a Jaguar, a BMW and a Mercedes-Benz, as well as a luxury flat.
If the woman fails to comply with the civil court ruling, the man will have to take further action to compel her.