A Japanese monk is suing his temple, claiming he was forced to work non-stop catering to visiting tourists and that the heavy workload gave him depression, his lawyer said on Thursday.

The monk in his forties is seeking 8.6 million yen ($78,000) from his temple on Mount Koya, a World Heritage Site also known as Koyasan that is regarded as one of the most sacred Buddhist sites in Japan.

The plaintiff began working at a temple there in 2008 and became depressed around December 2015, according to his lawyer Noritake Shirakura.

"If you work as a monk, too often you work without work-hour management," Shirakura told AFP.

"You provide labour, but you are told it's part of religious training. And if it's training, you must endure even it causes you significant hardship."

"Through this case, we will argue that such a notion is outdated," he said.

Shirakura declined to name his client or the temple being sued, saying the man wanted to preserve his anonymity so he could eventually return to his job or find a position elsewhere in the small community of Buddhist monks.

The case argues that the monk was forced to perform paid labour far beyond his spiritual duties, and at times worked for more than two months straight.