An apparatus includes a process chamber, a stage, a shower head, a plasma generation circuit, and a partition wall. The stage places a substrate. The shower head faces the stage and supplies process gas to the substrate. The plasma generation circuit generates plasma between the shower head and the stage. The partition wall isolates a first space between the shower head and the stage from a second space on a side of the shower head opposite to a side of the stage with a predetermined first gap, such that a pressure in the second space is higher than a pressure in the first space in a state where the process gas is supplied from the shower head, a gas different from the process gas is supplied to the second space, and an inside of the first space is evacuated.