According to the present invention, a thin film having a desired thickness is formed on an inner sidewall of a step with excellent step coverage in a film forming step and an etching step at least once, respectively. In an embodiment of the present invention, a target material is deposited on a substrate (17) having a concave step (31, 32) having an opening width or opening diameter of 3 μm or less and an aspect ratio of 1 or more. At this time, a film forming method according to the present invention has a first step of depositing a thin film onto a bottom (33) of the step (31, 32) and a second step of forming a film on an inner sidewall (34) of the step (31, 32) by re-sputtering the thin film deposited on the bottom (33) and the pressure in a process chamber in the second step is set lower than that in the process chamber in the first step and the ratio of anode power to cathode power in the second step is set greater than the power ratio in the first step.