A substrate processing apparatus includes: a substrate holder that holds and processes a substrate; a nozzle that ejects a processing liquid to the substrate held by the substrate holder; a conductive pipe connected to the nozzle and configured to supply the processing liquid to the nozzle; a processing liquid supply that supplies the processing liquid to the nozzle via the conductive pipe; a ground line that connects the conductive pipe and a reference potential; a liquid receiver provided around the substrate holder and configured to receive the processing liquid ejected from the nozzle; an electrode provided close to the liquid receiver; a voltage source configured to apply a voltage to the electrode and impart a potential difference between a liquid contact surface of the liquid receiver and the reference potential; and an ammeter configured to measure a current value of a current flowing through a charge moving path.