To provide a suction and exhaust pump to accurately and continuously measure an amount of removed water by composing a mechanical structure having no sliding abrasion part by interposing an airtight film, without requiring a suction and exhaust valve.

Cylinders 2, 2 having the same capacity are horizontally placed face to face on the right and left sides of a driving part 1, a rotation shaft 30 rotated clockwise and counterclockwise by a motor PM is extended in the driving part and ball screws 27, 27 are formed on the right and left extended part of the rotation shaft 30, ball nuts 32, 32 which follow the right and left ball screws of the rotation shaft are fixedly provided through a bearing 28 in the insertion holes at the centers of a pair of pistons 31, 31 relatively moving in the right and left cylinders, the bottom part of a cylindrical diaphragm D covering each piston 31 is fixed to the head part of the piston 31 and its peripheral ends are fixed to the sides of cylinders 2, 2 with its peripheral parts folded back in order to form right and left measuring compartments 42, 42 having the same capacity, and suction and exhaust is alternatively carried out at a designated quantity from the suction and exhaust hole 43 of each measuring compartment 42.