An insufflation device includes: a gas feeding conduit for feeding a predetermined gas which is fed from a gas supply source into a body cavity; and a processor. The processor measures a gas feeding time period until a predetermined amount of the gas is fed according to a set pressure, measures a pressure in the body cavity, calculates a gas discharging time period based on the set pressure and a measurement result of the measured pressure; and adjusts a gas feeding flow rate of the gas according to a difference between the measured gas feeding time period and the calculated gas discharging time period.