In a rotary magnet sputtering apparatus, a target consumption displacement quantity is measured, and corresponding to the measurement results, a distance between a rotating magnet group and a target is adjusted, and uniform film forming rate is achieved over a long period of time so as to reduce the change of a target surface due to consumption of the target and to reduce the change of the film forming rate with time. An ultrasonic sensor or a laser transmitting/receiving device may be used as a means for measuring the consumption displacement quantity of the target.