To improve a workability during assembling, and to facilitate introduction of automatization of assembling in a diaphragm pump.

On the top surface of a crank 4 to which an output shaft 2a of a motor 2 is journaled, a ring shaped engagement groove 5 having a center on the output shaft 2a is provided. A drive shaft 9b is integrally formed on a drive body 7. A lower end portion 9c of the drive shaft 9b is engaged in the engagement groove 5 to incline the axis 9d. The crank 4 rotates to engage the engaging part provided in the engagement groove 5 with the lower end portion 9c, so that the drive shaft 9b rotates following the rotation of the crank 4 while the axis 9d changes in the inclination direction. Accordingly, a diaphragm section 12a attached to a drive element 7a of the drive body 7 moves vertically, to contract/expand a pump chamber 18, thereby causing a pumping action.