A Seicomart convenience store employee in the regional capital Sapporo told local police a man was behaving aggressively with something looking like a kitchen knife before 0700 local time (2200 GMT), according to NHK, Reuters reported.
Three employees in their 40s to 60s were stabbed and injured, with a man in his 40s taken to the hospital where he later died. Two others, a man and a woman, remained conscious, NHK said, citing police.
An unemployed 43-year-old local was arrested on the spot on suspicion of attempted murder, NHK added.
In January, three men were injured in a stabbing incident in Akihabara tourism hotspot in Tokyo but public violence remains low in Japan.