Hiroshi Fujiwara, 81, allegedly said he was “tired” after 40 years looking after disabled Teruko, 79.
Police said he drove his wife to the harbor saying he wanted to go for a walk in their hometown Oisu, 35 miles south of Tokyo, Japan.
He then wheeled her chair along the pier and tipped her into the sea at 5.30pm last Wednesday.
Afterwards he drove to his eldest son’s house nearby and confessed what he had done, reports daily paper Asahi Shimbun.
Police said the son called them at 7pm saying: “My father said he pushed my mother (into the sea).”
Meanwhile a fisherman had reported seeing a body floating in the sea.
Teruko was recovered from the water and taken to hospital but was already dead.
Unemployed Hiroshi was arrested the next day and reportedly admitted his crime.
He said he was “tired” of caring for his wife, who lost the ability to use her legs around four decades ago.
The couple reportedly lived alone in an apartment in the seaside town and had no other help.
A neighbour in the block of flats said she was shocked.
She said: “He is friendly and often gave a ride to his wife, who I understand was bed-ridden.
“He was devoted to his wife, and there was nothing to suggest (he could kill her), but I guess he was struggling inside.”