A film depositing apparatus comprises: a rotatable drum within a chamber around which a substrate is wrapped in a specified surface region; a film depositing unit comprising a film depositing electrode spaced facing to a surface of the drum, and a feed gas supply section supplying a feed gas for forming a film into a gap between the drum and the film depositing electrode; and an exhaust unit that exhausts the gap between the drum and the film depositing electrode during film formation by the film depositing unit so as to forcibly discharge the feed gas, supplied into the gap by the feed gas supply section, through at least one of end portions of the gap upstream side and downstream side in a rotating direction of the drum uniformly over an entire region of the gap in a direction parallel to the axis of rotation of the drum.