To reduce a size of an outer diameter without impairing the performance of a diaphragm part by combining a case for storing a driving part, a cylinder part, a diaphragm main body and a cover body, and integrally fastening and fixing them by using a plate spring or a rod-shaped spring.

This small size pump is formed by combining a case 3, a cylinder part 11, a diaphragm main body 14 and a cover body 20, and fastening and fixing them by a plate spring 40. A flange 20a of the cover body 20 is mounted for preventing a point of the plate spring 40 from removed from the cover body, and the periphery of a lower end face of the case 3 has the similar shape. The fixing is performed by the fastening with the plate spring 40, so that it can be simplified. Whereby the fastening and fixing state can be surely held in comparison with the fastening by a screw, even when the change of temperature is repeated by the operation and stop or the like, of the pump.