To provide a metering pump device capable of preventing a fluid from dripping out of an outlet and the fluid from leaking out of the fixed part of the base end portion of a dome-like elastic member and also capable of accurately maintaining constant the discharge volume of the fluid for each pressing down operation of the dome-like elastic member.

In a first valve mechanism B1 installed near the inlet part of a fluid passage, a seal part is formed of a first valve seat part 15a in which a peripheral edge shape passed through a first partition wall part 15 is formed at the end part of a circular first through-hole 15h and the surface of a ball-like first valve element 3 disposed on an intermediate chamber Cm side. In a second valve mechanism B2 installed on the discharge side apart a specified distance from the first valve mechanism, a seal part is formed of a second valve seat part 41s in which a peripheral edge shape passed through a second partition wall part 41 is formed at the end part of a circular second through-hole 41h and the curved surface of a second valve element 4 disposed on the discharge side. In addition, an energizing spring 5 energizing the second valve element in the direction of the second valve seat part is installed in the device.