Diaphragm pump

A diaphragm pump includes: a volume changing member which changes the volume of a fluid chamber; a diaphragm member fixed in a stretched state and arranged separate from the fluid chamber, the diaphragm member having a pair of electrodes and a stretch film formed of dielectric elastomer, and the diaphragm member driving the volume changing member in a forward movement direction; a return bias member which drives the volume changing member in a backward movement direction; and a connection member which connects the diaphragm member and the volume changing member. In a low voltage state, the diaphragm member and the return bias member have driving force with respect to the volume changing member. The diaphragm member is arranged so as to be elastically protruded in the backward movement direction compared to the stretched state, and an inclination angle of the diaphragm member in the low voltage state with respect to that in the stretched state is set to 45° or greater in a cross section along a reciprocal movement direction.