a received signal phase detecting circuit in provided in which the circuit scale is small . the circuit functions so as to capture a frame synchronizing signal from a demodulated baseband signal , extract a symbol stream during the period of frame synchronizing signal from the demodulated baseband signal through delay circuits at a timing matching the bit stream of the captured synchronizing signal , rotating the phase of a corresponding symbol extracted from the symbol stream when the big in the bit in the bit stream is logic “ 0 ” by 80 °, outputting the symbol after the phase rotation and a corresponding symbol extracted from the symbol stream when the bit in the bit stream is logic “ 1 ” from a 0 °/ 180 ° phase rotating circuit , operating the cumulative average of the output from the 0 °/ 180 ° phase rotating circuit for a specific period through cumulative averaging circuits , rotating the phase of the outputs therefrom through a 22 . 5 ° phase rotating circuit , and determining the phase of the output therefrom by a phase determining circuit .