PURPOSE: To provide the driving device in which size of a pump mechanism device itself is small, a distance between the left and the right is small, matching to a living body is excellent, durability is satisfactory and a problem of an anti-throm-bus property can be settled.

CONSTITUTION: The objective driving device for a displacement pump of two systems is constituted so that a long rectangular plate spring 1 fitted in a curved state to a first fitting part A and a second fitting part B of a frame body 3, a part to be operated 1b extended from the plate spring 1 and an operating means 6 for operating the part 1b move to a first housing 4 side and a second housing side 5, by which the plate spring 1 is switched alternately to the second housing side 5 and the first housing 4 side, and by pressing a first diaphragm 4a and a second diaphragm 5a, a fluid is transferred.