A substrate processing apparatus includes a mounting stand installed to rotate about a rotation shaft extending along a rotary shaft of a rotary table and configured to hold a substrate, and a magnetic gear mechanism including a driven gear configured to rotate the mounting stand about the rotation shaft and a driving gear configured to drive the driven gear. The driven gear is connected to the mounting stand via the rotation shaft and installed to rotate in such a direction as to rotate the mounting stand. The driving gear is disposed in a state in which the driving surface faces the driven surface passing through a predetermined position on a movement orbit of the driven gear moving along with the rotation of the rotary table.