A high-frequency switch circuit common to a plurality or frequency bands comprises a first high-frequency switch connected to first high-frequency signal input and output terminals and adapted to pass transmission signals of a first or a second frequency band and block received signals of the first and second frequency band; and a demultiplexer has a first high-frequency circuit which consists of a first phaser connected to the first terminal and a first bandpss filter succeeding to the first phaser, and a second high-frequency circuit which consists of a second phaser connected to the first terminal and a second bandpass filter succeeding to the second phaser. The transmission line in the first phaser has a line length such that the input impedance of the first high-frequency circuit is substantially open in the pass band of the second bandpass filter, whereas the transmission line in the second phaser has a line length such that the input impedance of the second high-frequency circuit is substantially open in the pass band of the first bandpass filter. Thus, the high-frequency switch circuit passes one of thc received signals of the first and second frequency bands and blocks the other.