To provide a substrate processing device having a good yield, by reducing the frequency of forcedly suspending operation of the device due to decrease of a processing liquid in a processing liquid supply unit to effectively use the processing liquid.

The substrate processing device comprises a plurality of liquid processing units 12 for liquid-processing the substrate, a substrate conveying means carrying in and out the substrate to a plurality of liquid processing units 12, the process liquid supply unit 13 supplying the process liquid to a plurality of the liquid processing units 12, and a level gauge 161 detecting the remaining amount of the processing liquid in a processing liquid storage tank 16 of the processing liquid supply unit 13. When the remaining amount of the processing liquid in the processing liquid storage tank 16 detected by the level gauge 161 is lower than a predetermined amount, the carrying-in of the substrate to the liquid processing unit 12 is stopped.