A substrate processing apparatus comprises a first treatment device for performing a first treatment on a sheet-like substrate conveyed in the long belt direction; a second treatment device disposed, staggered with respect to the first treatment device, in a direction intersecting the conveying direction of the sheet-like substrate and configured to perform a second treatment on the sheet-like substrate; a third treatment device, which is provided with a carrying-discharge unit allowing two rows of sheet-like substrates to pass through together in a way of being spaced apart, and to perform a third treatment on the sheet-like substrate after the first treatment, or the sheet-like substrate after the second treatment; and a conveying device comprising: a first conveying unit to convey the sheet-like substrate in the long belt direction after the sheet-like substrate passes the first treatment device and moves toward the third treatment device; a second conveying unit to convey the sheet-like substrate in the long belt direction after the sheet-like substrate passes the third treatment device and moves toward the second treatment device; and a third conveying unit to convey the sheet-like substrate in the long belt direction after the sheet-like substrate passes the second treatment device and moves toward the third treatment device.