A substrate processing apparatus includes a polishing section and a transport section. The polishing section has a first polishing unit, a second polishing unit, and a transport mechanism. The first polishing unit has a first polishing apparatus and a second polishing apparatus. The second polishing unit has a third polishing apparatus and a fourth polishing apparatus. Each of the first to fourth polishing apparatuses has a polishing table to which a polishing pad is mounted, a top ring, and auxiliary units that perform a process on the polishing pad during polishing. Around the polishing table, a pair of auxiliary unit mounting units for mounting the respective auxiliary units in a left-right switchable manner with respect to a straight line connecting a swing center of the top ring and a center of rotation of the polishing table is provided at respective positions symmetrical with respect to the straight line.