A substrate processing apparatus comprising a standby chamber for supporting a substrate in a substrate support jig and maintaining the substrate in standby, a transfer chamber, and a chamber housing a carrier load mount for loading a carrier storing the substrate, which are provided in order along a length direction from the rear side within a case having a maintenance opening for entry of maintenance personnel into the chamber housing the carrier load mount from outside the case, and a processing chamber provided above the standby chamber for processing the substrate, wherein the line segment joining the center of the substrate supported in the substrate support jig, with the center of the substrate on the carrier loaded in the carrier load mount, when at rest position, is offset to an offset side along the width direction with respect to the center line passing through the center of the case width;
- and an opening section disposed in a wall isolating the transfer chamber from the chamber housing the carrier load mount to form an air-tight seal, and a door for opening and closing the opening section are provided at the front side of the transfer chamber on the side along the width direction which opposes the offset side along the width direction and for entry of maintenance personnel into the transfer chamber.