To form a flat coating film with a smooth surface on a substrate to be treated.

In this resist coating, an ultrasonic irradiation part 160 immediately after a resist nozzle 154 on the switched-on state is transferred together with the resist nozzle 154 while ultrasonic waves being applied toward the vicinity of a boundary E between band-shaped resist liquid films R(1) and R(2) in the second-time and onward Y-direction scannings. Since the resist liquid is reduced in viscosity or fluidized in the vicinity of boundary between both the band-shaped resist liquid films R(1) and R(2) by the ultrasonic irradiation-scanning of the ultrasonic irradiation part 160, the surfaces of the two liquid films are made uniformly smooth in a direction (horizontal direction) parallel to the substrate surface to remove unevenness.