Reduction in cooling rate of a substrate having a lower temperature is suppressed because the substrate having a lower temperature is not affected by radiant heat of a substrate having a higher temperature while cooling a plurality of substrates in a cooling chamber. The substrate processing apparatus includes a load lock chamber configured to accommodate stacked substrates; a first transfer mechanism having a first transfer arm provided with a first end effector, and configured to transfer the substrates into/from the load lock chamber at a first side of the load lock chamber; a second transfer mechanism having a second transfer arm provided with a second end effector, and configured to transfer the substrates into/from the load lock chamber at a second side of the load lock chamber; a barrier installed between the substrates to be spaced apart from the substrates supported by a substrate support provided in the load lock chamber; and a barrier auxiliary unit installed between the substrate support and the barrier, wherein the barrier auxiliary unit is installed at places other than standby spaces of the end effectors.