PURPOSE: To make it possible to supply two high frequencies to an irradiation coil without a magnetic core, by connecting the output of the first high frequency source to a load directly and by connecting the output of the second high frequency source and the load through a coaxial line.

CONSTITUTION: This unit transmits large-amplitude high-frequency pulse A from high frequency generator 6 and small-amplitude high-frequency pulse B from high frequency generator 7 to a load, and coaxial line 8 has the length of the approximate quarter of the wave length of high frequency A, and the output of high frequency generator 7 is grounded through the circuit where diodes are connected in antiparallel. When circuit 9 is turned on during generation of large-amplitude pulse A, coaxial line 8 has an infinite impedance to supply large-amplitude pulse A to the load without loss. Meanwhile, during no generation of large-amplitude pulse A, small-amplitude pulse B is supplied to the load through coaxial line 8 because circuit 9 is held in the turning-off state.