Substrate processing apparatus including light receiving device and calibration method of light receiving device

A substrate processing apparatus comprising:

• a chamber configured to contain a stage;
• a light receiving device configured to receive light inside the chamber;
• a substrate transfer apparatus that includes a shaft and a rotation arm configured to rotate with rotation of the shaft and is configured to supply a plurality of light beams having different amounts of light to the light receiving device;
• a light source;
• and
• the rotation arm in plurality, wherein
• the plurality of rotation arms are formed of a light transmitting material that transmits light,
• a plurality of holes are provided on a side face of the shaft, the plurality of holes are configured to pass light of the light source, and
• the plurality of rotation arms are provided in one-to-one correspondence with the plurality of holes.