Abstract: The object of the present invention is to provide a sealer gun in which even an operator having no expert skill can easily conduct application by optionally setting the bead width, and keep the application uniform from the initial stage to the final stage. In the sealer gun, the needle valve is moved backward by predetermined strokes by operating the trigger, and a sealer is spouted from the gap between the valve seat and the needle valve. In this instance, with the adjusting knob of the notch portion provided in the base portion of the gun body, the position-adjusting member is moved back and forth, and the moving-backward stroke of the needle valve is controlled. The tapered portion 8b is formed at the tip of the needle valve, and the orifice member is provided in the sealer passage in the downstream of the valve seat so as to absorb the pulsating pressure variation of the sealer.