A substrate processing apparatus includes a chamber, a substrate holding unit, an elevated/lowered member, and an elevation/lowering driving unit. The chamber includes a base plate having an upper surface that defines a housing space. The substrate holding unit is housed in the housing space, is placed on the upper surface of the base plate, and holds a substrate. The elevated/lowered member is elevated and lowered inside the housing space. The elevation/lowering driving unit drives the elevation and lowering of the elevated/lowered member. The elevation/lowering driving unit includes a driving source, disposed higher than a lower surface of the base plate, and an elevating/lowering head, which is connected to a guard and is moved vertically by the driving source within a movable range in which an entirety of the head is positioned higher than the lower surface of the base plate.