BELLOWS PUMP DEVICE

A control unit 6 of a bellows pump device 1 determines whether or not a second bellows 14 (first bellows 13) is in a predetermined expanded state when the first bellows 13 (second bellows 14) contracts to a mid-contraction state, on the basis of respective detection signals of a first detection unit 29 and a second detection unit 31, and when a determination result of the determination is negative, the control unit 6 performs next pressure increase control of controlling a second electropneumatic regulator 52 (first electropneumatic regulator 51) such that an air pressure of a pressurized air to be supplied to a second suction-side air chamber 26B (first suction-side air chamber 26A) of a second driving unit 28 (first driving unit 27) at next expansion of the second bellows 14 (first bellows 13) is increased.