A film deposition apparatus includes a turntable provided in the chamber and having on a first surface a substrate receiving area in which a substrate is placed; first and second reaction gas supplying portions supplying first and second reaction gases to the first surface, respectively; a separation gas supplying portion provided between the first reaction gas supplying portion and the second reaction gas supplying portion and supplying a separation gas that separates the first reaction gas and the second reaction gas; an evacuation port that evacuates the chamber; a space defining member provided for at least one of the first and second reaction gas supplying portions and defining a first space between the at least one of the first and second reaction gas supplying portions and the turntable and a second space so that the separation gas is likely to flow through the second space rather than the first space.