Among arbitrary positions on the course of a sealing gun, a position ahead of and separated from the arbitrary position in the moving direction of the sealing gun by a given distance, where an application part falls within a given allowable size in a direction perpendicular to the moving direction on the basis of the sealing gun, is a first position, and a position where the application part is deviated from the allowable size is a second position. A control device corrects the course of the sealing gun that is defined by an operation plan, based on the shape of the application part measured in a measurement point located at the first position.