PURPOSE: To provide the pressurizing pump of a hemadynamometer of an attachment type and large capacity which can make easy measurement in a short period of time and has high suction efficiency and excellent check counterflous check function.

CONSTITUTION: The suction side of the pressurizing pump is constructed by disposing a synthetic rubber sheet 4 adhered to an end plate 3 in tight contact with the end face of flexible bellows 1 having an aperture 2 at the end face and the discharge side is constructed by disposing a ball 13 pressed to an inflow port 8 side by a spring 12 in a cover 7 having an inflow port 8 facing to the space in the bellows 1 and an outflow port 11 facing the outside and interposing an O-ring 14 between the ball 13 and the inside surface of the cover 7 to tightly seal the ball and the cover. The air in the bellows 1 is discharged from the outflow port 11 by compressing the bellows 1. The outdoor air is sucked into the bellows 1 through an aperture 2 of the end face of the bellows 1 from the spacing between the synthetic rubber sheet 4 and the end face of the bellows 1 in the process of restoring of the bellows 1 by expanding.