To perform the use of either a pressure pump or a pressure reduction pump by preventing deformation of the vicinity of the connection to the drive part of a diaphragm part by a method wherein the upper half part of the cup- form wall of a diaphragm part forms a thick section part and a protrusion part protruding into a pump output is formed on a driving part.

The upper half part of the cup-form wall of a diaphragm part 15 forms a thick section part, and a protrusion part 16a protruded in a diaphragm part 15 (the cup-form inside) is formed at a driving part 16. When, through rotation of a motor 1, a drive body 7 is caused to effect precession, the driving part 16 effects a piston movement with a specified phase difference and pump operation is performed. In which case, the driving part 16 is lowered and a pressure in a pump chamber 28 is reduced, and a force toward the pump chamber side is exerted on the wall surface of the cup-form part of the diaphragm part 15, no deformation occurs owing to the thick section part. Further, deformation of the periphery of the diaphragm part 15 is suppressed to a minimum by the protrusion part 16a of the driving body 16.