A piece gun for spraying includes a base body. A trunk portion is provided with a storage area for containing a coating liquid. The trunk portion is positioned within the base body. A head portion is connected to the trunk portion. The head portion is provided with a writing member for discharging the coating liquid. A first air passage surrounds at least the head portion of the trunk portion. A second air passage is operatively connected to a source of high pressure fluid. A switching valve includes an operational member for manual actuation and a working member operatively connected to the operational member. The working member initially operates the switching valve to connect the second air passage to the atmosphere during an early stage of operation of the operational member. The working chamber communicates the second air passage with the first air passage during a latter stage of operation.