A multi-channel radio frequency generator for high-frequency thermal treatment is used in combination with a plurality of electrodes. The multi-channel radio frequency generator includes an oscillator for producing a high-frequency, a waveform modulator part for modulating an waveform of the high-frequency generated by the oscillator, first to third amplifying channels for amplifying the high-frequency outputted from the waveform modulator part to have a root mean square output of 30-200 Watts and then supplying the root mean square output to the electrodes, a channel selection part for allowing a user to select one or more of the first to third amplifying channels, a key part for enabling the user to set a voltage, a current and an impedance for the first to third amplifying channels, and a microcontroller unit for controlling a power, a time and a phase of the high-frequency outputted from each of the first to third amplifying channels.