The incident occurred near a station called Dainhat in West Bengal, about 130 km from Kolkata. The 'Up Katwa Local' was ferrying passengers from Howrah station to Katwa town in Burdwan district.
Around noon, eyewitnesses suddenly saw the driver fall off the train which came to a halt.
The train was about to change tracks when the incident happened.
Mr I Haldar, the train driver now in hospital, told authorities he suddenly felt very sick and became unconscious. He received some serious head injuries due to the fall, according to Mr R Mahapatra, chief public relations officer, Eastern Railways.
Two other trains were delayed because of the incidence.
The railways will examine Mr Haldar for health conditions. According to Mr Mahapatra, he was fine when he boarded the train at Howrah.
This is not the first such incident. In July, the 'Up Sonarpur Local' rammed into a platform guard-wall at Sealdah station in Kolkata. Medical tests indicated the driver was suffering from work-related stress.