To provide a method for detecting machining position deviation for accurately detecting the machining position deviation caused by response delay of a servo motor driven based on a synchronizing signal of a main motor.

In this method, a workpiece 10 is carried to a machining position by a carrying means 11 provided with the motor M1, a machining means 12 is operated by the servo motor M2 driven based on the synchronizing signal of the motor M1, and the machining position deviation when machining the workpiece 10 is detected. A pulse signal according to rotation amount of the motor M1 is determined by an encoder 2. A detection position for fixing the machining time by the machining means 12 is detected by a detection means 5. The machining position deviation by the machining means 12 is determined based on the counted number of the pulse signal corresponding to the machining time.