When a coating film is formed on a substrate, the inplane uniformity of the thickness of the coating film is enhanced to improve through put. Above the substrate, there are provided main and auxiliary nozzles separately movable, and monitoring means for monitoring the state of the surface of the substrate to detect the occurrence of an uncoated region on the surface of the substrate. On the basis of previously prepared coating data, a coating liquid is spirally applied on the substrate by the main nozzle. Then, if the monitoring means detects the occurrence of the uncoated region in a coated region in which the coating liquid has been applied by the main nozzle, a control part detects whether it is required to supply the coating liquid to the uncoated region. If it is required, the coating liquid is supplied to the uncoated region by the auxiliary nozzle. On the other hand, the portion of occurrence of the uncoated region has been grasped by the control part. If the uncoated region is continuously detected at the same place with respect to two substrates, it is determined that the setting of coating data is erroneous, and this is modified.