A film deposition apparatus includes a process chamber, a rotary table, a first reaction gas supply part disposed in a first process region and configured to supply a first reaction gas, a second reaction gas supply part disposed in a second process region apart from the first reaction gas supply part in a circumferential direction of the rotary table and configured to supply a second reaction gas, and separation gas supply parts disposed in a separation region between the first reaction gas supply part and the second reaction gas supply part and configured to supply a separation gas for separating the first reaction gas and the second reaction gas. The separation gas supply parts are configured to supply, in addition to the separation gas, an additive gas for controlling adsorption of the first reaction gas or for etching a part of material components included in the first reaction gas.