Tokyo: A Japanese woman hit out at corporate bosses this week, after her restaurant manager son died of a brain haemorrhage having done 200 hours of overtime in a month.

The case is the latest of of deaths a year officially determined to have been caused by the hardships of working for Japanese companies.

Takayuki Maezawa was the second employee at unlisted restaurant chain Skylark Co Ltd to die from overwork in the last four years.

"My son was an extremely responsible person, who could never refuse if asked to do something," the Asahi Shimbun quoted his 59-year-old mother as saying.

Maezawa, who worked at Skylark since 1991, usually left home around 7am and returned around 2am, taking only two or three days off each month.

"We accept the decision seriously and want to try harder to oversee our operations," Shunichi Ito, a spokesman for Skylark, said.

Death from overwork, known as 'karoshi', has long been a serious issue in Japan, where an average worker uses less than 50 per cent of paid holidays, according to data.

In the year to March 2008, the labour ministry determined 142 people died from overwork.