To provide an endless phase shifter where the number of kinds of hybrid circuits is reduced.

A 90° hybrid circuit 2 branches a signal S1 branched in phase with an input signal Si by a 90° hybrid circuit 1 further into signals S1a, S1b that are in phase and lagged by 90°. A 90° hybrid circuit 3 branches a signal S2 branched with a phase lag of 90° from the input signal Si further into signals S2a, that are in phase and lagged by 90°. Variable attenuators 7a, 7b and 8a, 8b respectively apply prescribed attenuation to the signals S1a, S1b and the signals S2a, S2b. A pair of 90° hybrid circuits 4, 5 receive the outputs of the variable attenuators 7a, 7b and 8a, 8b and cause an additional 90° phase delay to the signals delayed by 90° and synthesize them to output signals S3, S4. An in-phase hybrid circuit 6 synthesizes the signals S3, S4 in phase to provide an output signal So to which a prescribed phase shift is applied.