PURPOSE: To prevent the error rate of demodulated data of a PSK modulated wave form becoming worse against fading accompanied by a phase shift.

CONSTITUTION: A received electric field level detection part 1 detects the level of an IF signal S1 in synchronism with a sampling clock signal CL2 and outputs (n) received electric field level signals SO for every symbol. A phase error calculation part 6 receives a phase difference signal S5 and a demodulated signal S6 from the input side and output side of a multivalued decision part 5, and calculates and outputs the phase error as a phase error signal S7. A weighting part 8 multiplies the value of a phase error square signal S8 generated by a phase error calculation part 6 and an error squaring part 7 by the values of the received electric field level signals SO. A selector control part 9 detects the time when the value of the phase error square signal S9 weighted with the received electric field becomes minimum and outputs a select signal S10. A selector control part 9 selects one of (n) demodulated signals S6 according to the select signal S10.