DIAPHRAGM PUMP

A diaphragm pump (1) operates by receiving a pulsating pressure in a crank chamber (2a) of an engine (2). The diaphragm pump includes a low pressure side diaphragm (10) that operates by receiving a pulsating pressure, a high pressure side diaphragm (20) that sends fuel to an engine, and a connecting portion (30) that connects the low pressure side diaphragm and the high pressure side diaphragm to each other. An area of a high pressure side operating portion (20a) of the high pressure side diaphragm is smaller than an area of a low pressure side operating portion (10a) of the low pressure side diaphragm.