BELLOWS PUMP APPARATUS

Provided is a bellows pump device that allows an impact pressure generated when switching is made from suction of a working fluid to discharge of the working fluid, to be easily reduced even with an already-installed bellows pump. The bellows pump device supplies pressurized air to one air chamber (26) of two hermetic air chambers (21, 26) thereby to cause a bellows (13, 14) to perform expansion operation to suck a transport fluid, and supplies pressurized air to the other air chamber (21) thereby to cause the bellows (13, 14) to perform contraction operation to discharge the transport fluid. The bellows pump device includes: an electropneumatic regulator (51, 52) configured to adjust a first air pressure of the pressurized air to be supplied to the one air chamber (26), and a second air pressure of the pressurized air to be supplied to the other air chamber (21); and a control unit (6) configured to control the electropneumatic regulator (51, 52) such that, at least at a time point of end of expansion during expansion operation of the bellows (13, 14), the first air pressure is lower than the second air pressure.