Substrate processing of a substrate is performed in a processing chamber and the evenness in in-plane film thickness is enhanced. An exhaust unit exhausts the atmosphere in the processing chamber and a processing gas is supplied that is excited by an exciting unit. A rotational drive unit horizontally rotates a support unit that supports a mounting substrate on which the substrate is mounted; and a coolant supply/discharge unit is connected to the lower end of the support unit through a connecting unit. The substrate mounting unit has a coolant circulation path therein. The support unit includes a first coolant flow path for passing coolant through the coolant circulation path. The coolant supply/discharge unit includes a second coolant flow path. The connecting unit connects the first coolant flow path and the second coolant flow path together and is provided outside the processing chamber.