The 80-year old man and his wife had been confined to their cabin on the Diamond Princess for 11 days.
His wife told the French radio station RTL that on receiving the test result he was taken to a hospital whose address she didn't know.
She said her husband showed no symptoms of the illness, but further tests were planned to confirm the diagnosis.
She says they both took all the precautions but still her husband caught the virus.
Almost 220 people onboard the cruise ship off Yokohama have tested positive to the coronavirus.