A plasma irradiation device has a gas flow channel and an electric field generation section and is provided in a handpiece. The gas flow channel is a flow channel for supplying a gas from the outside of the handpiece to a distal end portion of the acting member. The electric field generation section has a first electrode portion, a second electrode portion, and a dielectric member and is disposed in the gas flow channel. The electric field generation section generates an electric field in a space within the gas flow channel by using a potential difference between the first electrode portion and the second electrode portion, thereby producing low-temperature plasma discharge.
