A substrate processing apparatus includes: a cylindrical shaped chamber configured to accommodate a substrate; a movable electrode capable of moving along a central axis of the cylindrical shaped chamber within the cylindrical shaped chamber; a facing electrode facing the movable electrode within the cylindrical shaped chamber; and an expansible/contractible partition wall connecting the movable electrode with an end wall on one side of the cylindrical shaped chamber. In the substrate processing apparatus, a high frequency power is applied to a first space between the movable electrode and the facing electrode, a processing gas is introduced thereto, and the movable electrode is not in contact with a sidewall of the cylindrical shaped chamber. At least one low dielectric member is provided in a second space between the movable electrode and the end wall on one side of the cylindrical shaped chamber.