To provide a helium leak tester which can perform test in a short time even when the member of a specimen itself discharges a gas significantly.

A specimen W composed of a resin part Wa and a non-resin part Wb and previously encapsulating helium gas as a probe gas is held while vacuum sealing the side face of the resin part Wa having high gas discharge rate with upper and lower O-rings 10. Since the resin part Wa of the specimen W separated by two O-rings 10 is not exposed to vacuum in a chamber 2, gas is not discharged from that part.