PURPOSE: To attain mass production for reduction of cost by attaching a cover having an annular wall of the cylindrical structure in a case whose one side surface opens and which incorporates an electric motor and a pumping device, and forming the cover so as to reinforce the opening of the case.

CONSTITUTION: This suction pump mechanism including a fluid reservoir 4 for the draw-off of waste water for medical use is provided with a suction pump 2 which is the part thereof, a cover 10, and a case 12 mounted on the cover 10 by means of a fastener 14. The cover 10 is a plastic mold having the cylindrical of structure of an annular wall 16 and integrally-formed with a pair of support bases 18 to which an electric motor 20 is attached. The electric motor 20 drives a bellow 26 through a reciprocating push rod 28. When the bellow 26 is driven in the direction that volume expands, air is sucked through a valve mechanism 34, and when the bellow 26 is driven in the direction opposite thereto, air whose pressure is raised is discharged through a fluid chamber 8.