The elderly patient's right leg was removed instead of his left, with the mistake only discovered two days later.
On Wednesday, the court in Linz found the 43-year-old guilty of gross negligence and fined her €2,700 (£2,296).
The widow of the patient, who died before the case came to court, was also awarded €5,000 in damages.
The patient attended the clinic in Freistadt last May to have his leg amputated but the surgeon marked the wrong limb for amputation, AFP news agency reports.