A first shift unit (14) that shifts an amplitude value of the I baseband signal and an amplitude value of the Q baseband signal in a lower direction by the predetermined number of bits so that the predetermined number of lower bits thereof have a value after a decimal point, a first rounding unit (15) that rounds-to-even the amplitude value of the I baseband signal and the amplitude value of the Q baseband signal shifted by the first shift unit (14) with a rounding width of 1 in decimal notation, and a first averaging unit (16) that respectively calculates a time average of the amplitude value of the I baseband signal and the amplitude value of the Q baseband signal rounded by the first rounding unit (15) are included.