A high-frequency power source device includes switching element groups having a configuration in which a plurality of switching elements turned on/off cyclically are connected in parallel. One parallel connection terminal of the switching element group is connected to a positive electrode terminal of a DC power source, and one parallel connection terminal of the switching element group is connected to a negative electrode terminal of the DC power source. Respective other parallel connection terminals of the switching element groups are connected via a reactor. A pulse voltage that appears at opposite ends of the reactor due to a cyclic on/off operation of the switching element groups is applied to a load through a coaxial cable and a matching circuit.