To enable a definite quantity of liquid to be injected into a spraying can simply with a good measurement.

One end of a shaft 19 to be slid by rotation of a valve opening / closing lever 14 is mounted in an eccentric position of the valve opening / closing lever 14 formed at one end of a T-shaped external pipe 13. The other end of the shaft 19 is attached to a valve mounted at the other end of the T-shaped external pipe 13, and a cap 22 to be screwed into an outlet port of a liquid tank is mounted on the other end of the T-shaped external pipe 13. A transparent metering tank 29 is mounted at a lower end of the T-shaped external pipe and a valve mechanism to be closed normally with elastic force of a coil spring 32 and opened when a slide member 31 is pushed up against this coil spring 32 is provided at a lower end of the metering tank 29.