This disclosure of a liquid treatment device includes a first metal electrode having a part disposed in a reaction tank into which a water being treated is filled, a second metal electrode disposed in the reaction tank, an insulator having an opening portion disposed to surround the first metal electrode so that a closed space is formed. A bubble is generated from the closed space to the water being treated via the opening portion. The liquid treatment device also includes a gas supply device that supplies the space with a gas for generating the bubble, and a power supply that applies a voltage between the first metal electrode and the second metal electrode.