In a magnetron sputtering apparatus configured such that a magnetic field pattern on a target surface moves with time by means of a rotary magnet group, it is to solve a problem that the failure rate of substrates to be processed becomes high upon plasma ignition or extinction, thereby providing a magnetron sputtering apparatus in which the failure rate of the substrates is smaller than conventional. In a magnetron sputtering apparatus, a plasma shielding member having a slit is disposed on an opposite side of a target with respect to a rotary magnet group. The distance between the plasma shielding member and the substrate is set shorter than the electron mean free path or the sheath width. Further, the width and the length of the slit are controlled to prevent impingement of plasma on the processing substrate. This makes it possible to reduce the failure rate of the substrates.