In a film deposition apparatus, a first separation gas is discharged from a separation gas supplying portion to a separation area between a first process area to which a first reaction gas is supplied and a second process area to which a second reaction gas is supplied. A heater is provided to heat the turntable by radiation heat. An outer sidewall member is provided in a bottom part of a vacuum chamber to surround the turntable in an area where the heater is provided. A space forming member is provided between the separation areas adjacent to each other in a rotating direction of the turntable and extending from the outer sidewall member to form a narrow space between the turntable. A purge gas flows from a lower side of the turntable to an area outside the turntable in a radial direction through the narrow space.