An atomic layer film forming apparatus includes a plurality of gas supply pipes (121-123) for supplying a source gas to a film forming chamber (101), and an exhaust portion (105) for evacuating the inside of the film forming chamber (101). Valves (131-133) are attached to the gas supply pipes (121-123), respectively. In the film forming chamber (101), film forming chamber monitors (141-149) are arranged to measure a state in the film forming chamber (101). Based on the results of measurement by the film forming chamber monitors (141-149), a controller (107) controls the openings or opening times of the valves (131-133). The atomic layer film forming apparatus can improve gas uniformity when a plurality of gas supply ports are used.