At least 17 other passengers in the accident which occurred when the Saudia Paribahan vehicle swerved off the road in an attempt to prevent a collision with a jaywalker on the Patiya Bypass in Indrapole around 12pm on Saturday, according to the fire service.
The victim was identified as Moulvi Md Shamsu, 55, who owned a shop in the port city's Lucky Plaza.
The bus was heading to Chattogram city, said Shourov Bhuiyan, station officer of Patiya Fire Service.
"A pedestrian was jaywalking on the bypass when the driver slammed the brake to avoid running him over. The bus consequently veered out of control and rolled over into the paddy field."
Shamsu died on the spot, said Shourov.
Police and fire service personnel rescued 17 passengers until 1.30pm. They have been sent to a local hospital.