A diaphragm pump includes a quick discharge valve unit that comprises a vessel including a supply passage, a check valve seat, a delivery passage and a discharge passage, and an elastic member configured to partition an internal space of the vessel into an input-side space connected to the supply passage and an output-side space connected to the delivery passage and the discharge passage. The elastic member includes a check valve body to prevent an inflow of air from the output-side space to the input-side space, and a discharge port valve body configured to close the discharge passage when air is supplied to the input-side space through the supply passage. The vessel includes a connecting path having a sectional area smaller than an area of a section of the supply passage, and configured to release pressurized air in the input-side space to an outside.