A pathogen and pest exterminating device that can efficiently exterminate pathogens and pests in a shorter time. One electrode includes a part to be inserted into a reaction vessel, and other electrode is arranged in a position that opposes the insertion part. A water supply unit is provided to supply water to the reaction vessel through the insertion part, and a gas supply unit provided of supplying gas, which will become plasma, to the reaction vessel. A power supply unit is provided to be capable of applying voltage between the insertion part and the other electrode such that OH radicals are generated inside the reaction vessel to which the water and the gas are supplied. The insertion part is formed in a shape that restricts, between itself and the other electrode, a flow rate of water from the water supply unit such as a coil, waveform, or mesh shape.
