To discharge a fluid at high speed and with a high degree of accuracy by simplifying prevention of a switching valve leakage.

There is provided a constant-fluid-flow discharging method with switching communication between a cylinder 2 and a storage container 14 or a nozzle 15 by means of the switching valve. In a backing motion of a plunger rod 3 of the cylinder, the cylinder and the storage container are made to communicate with each other by the switching valve and sucking force is generated in a flow channel of the switching valve communicating with the cylinder to suck the fluid from the storage container to the cylinder. On the contrary, in an advancing motion of the plunger rod of the cylinder, the cylinder and the nozzle are made to communicate with each other by the switching valve and discharging force is generated in the flow channel of the switching valve communicating with the cylinder to discharge the fluid from the nozzle via a first flow channel of the switching valve, thus making the fluid flow into a second flow channel. Further, sealing force (an O ring) is generated depending on pressure of the fluid to be discharged. Thereby, the constant-fluid-flow discharging method prevents the switching valve leakage.