An upper processing liquid nozzle moves back and forth between a processing position above a substrate held on a spin chuck and a standby position outside a processing cup. Before a processing liquid is discharged from the upper processing liquid nozzle having moved to the processing position, a camera takes a discharge standard image of an imaging region including the tip of the upper processing liquid nozzle. Then, multiple monitor target images of the imaging region taken successively by the camera are compared sequentially to the discharge standard image to determine discharge of a processing liquid from the upper processing liquid nozzle. The discharge standard image is obtained for each process on a new target substrate. This eliminates influence of a substrate surface to appear as a background both of the monitor target image and the discharge standard image. Thus, discharge of a processing liquid can be detected reliably.