A liquid processing apparatus includes a processing tank, a liquid introduction port, a discharge portion, a first electrode, a second electrode, and a power supply. The liquid introduction port is disposed on a first end side of the processing tank, causes a liquid to swirl in the processing tank by introducing the liquid into the processing tank in a tangential direction of the processing tank, and generates a gas phase in a swirling flow of the liquid. The first electrode has a rod shape and is disposed at the first end on a central axis of the processing tank. The second electrode is disposed so as to be exposed to the discharge portion of the processing tank. A voltage is applied between the first electrode and the second electrode to generate plasma in the gas phase.