A multi-cylinder diaphragm pump is equipped with: a first case body having multiple pump chamber formation recesses capable of forming multiple pump chambers, and inflow-side communication grooves and outflow-side communication grooves which are provided in each of the pump chamber formation recesses and one end of each of which is connected to a corresponding pump chamber formation recess; a second case body having an inflow-side joint communication groove that is hydraulically connected to an intake port and that enables the other end of each of the multiple inflow-side communication grooves to communicate with each other, and an outflow-side joint communication groove that is hydraulically connected to an exhaust port and that enables the other end of each of the multiple outflow-side communication grooves to communicate with each other; and a packing member that is sandwiched between the first case body and the second case body, and covers the respective opening surfaces of the first case body and the sec
