To precisely form a thin coating film even in a dry state by forming a projecting part at the tip end part of a nozzle main body discharging a coating agent in the downstream side of base material travelling direction and changing an angle of the outside peripheral part of the projecting part in accordance with the coating thickness of the coating agent.

The coating agent is supplied from a coating agent supply port 19 while travelling the base material 18 from the back surface side to the front surface side. The coating agent is discharged from a nozzle opening 10 through a nozzle part 9 from a coating agent storing part 8. In such a case, the coating thickness of the coating agent is made thin by using the coating agent supply nozzle 1 formed so that the length of the projecting part 14, formed at the tip end part 13 of the front surface side nozzle half body 3, in the base material travelling direction is made short and the angle of the outer peripheral part 15 of the projecting part 14 is erected, that is the length of the projecting part in the base material travelling direction is set to about 0.5 mm and the angle of the outer peripheral part is formed square. As a result, the internal pressure of the coating agent supply nozzle 1 is increased and the coating agent is precisely discharged from the nozzle opening 10.