Diaphragm pump and valve plate thereof

A diaphragm pump, comprising:

• a valve seat, formed with a first receiving trough and a second receiving trough, the first receiving trough having a first runner gate, the second receiving trough having a second runner gate;
• a head cover, covering the valve seat;
• a pair of valve plates, one of the valve plates being disposed in the first receiving trough, and the first receiving trough having a geometric shape corresponding with a geometric shape of the valve plate;
• the other one of the valve plate being disposed in the second receiving trough, and the second receiving trough has a geometric shape corresponding with that of the valve plate;
• wherein the valve plate has a sealing part and at least one extending arm, the at least one extending arm is extended outwardly from a partial periphery of the sealing part, the sealing part has a geometric shape being bilaterally symmetrical, the at least one extending arm having an end shaped as a protrusion, a gap is formed between the valve plate the first receiving trough or the second receiving trough.