A likelihood generation circuit for generating a likelihood of a received symbol of received data modulated by a quadrature phase shift keying, QPSK, and an 8-quadrature-amplitude-modulation, 8QAM, modulation scheme, Z comprising: a received symbol phase rotation part configured to rotate J Z to a first quadrant of a constellation mapping diagram of the 8QAM modulation scheme, the phase of the received symbol of the received data modulated by the 8QAM modulation scheme bitmapped by being assigned one bit for selecting the inner circle or the outer circle of the constellation mapping diagram and two bits representing each quadrant thereof; a phase rotation adjustment part configured to rotate the phase of the received symbol of the received data modulated by the 8QAM modulation scheme on the inner circle or the outer circle of a symbol set of the received data modulated by the 8QAM modulation scheme; a first likelihood generation part configured to generate, by QPSK likelihood generation, a likelihood of the received symbol of the received data modulated by the QPSK modulation scheme, and a likelihood of the two bits, which represent each quadrant of the 8QAM constellation mapping diagram of the received symbol of the received data modulated by the 8QAM modulation scheme and processed by the phase rotation adjustment part; a phase rotation part configured to rotate, to the first quadrant of the constellation mapping diagram, the phase of the received symbol of the received data modulated by the 8QAM modulation scheme and processed by the Z phase rotation adjustment part and a second likelihood generation part configured to move, to symbol mapping positions of the QPSK modulation scheme, the received symbol of the received data modulated by the 8QAM modulation scheme and processed by the phase rotation part, by applying processing of offsetting and a constant multiplication to the received symbol having the phase rotated to the first quadrant, to thereby generate, by the QPSK likelihood generation, a likelihood for the bit representing whether the received symbol is on the inner circle or the outer circle of the symbol set modulated by the 8QAM modulation scheme. a received symbol phase rotation part configured to rotate J Z to a first quadrant of a constellation mapping diagram of the 8QAM modulation scheme, the phase of the received symbol of the received data modulated by the 8QAM modulation scheme bitmapped by being assigned one bit for selecting the inner circle or the outer circle of the constellation mapping diagram and two bits representing each quadrant thereof; a phase rotation adjustment part configured to rotate the phase of the received symbol of the received data modulated by the 8QAM modulation scheme on the inner circle or the outer circle of a symbol set of the received data modulated by the 8QAM modulation scheme; a first likelihood generation part configured to generate, by QPSK likelihood generation, a likelihood of the received symbol of the received data modulated by the QPSK modulation scheme, and a likelihood of the two bits, which represent each quadrant of the 8QAM constellation mapping diagram of the received symbol of the received data modulated by the 8QAM modulation scheme and processed by the phase rotation adjustment part; a phase rotation part configured to rotate, to the first quadrant of the constellation mapping diagram, the phase of the received symbol of the received data modulated by the 8QAM modulation scheme and processed by the Z phase rotation adjustment part and a second likelihood generation part configured to move, to symbol mapping positions of the QPSK modulation scheme, the received symbol of the received data modulated by the 8QAM modulation scheme and processed by the phase rotation part, by applying processing of offsetting and a constant multiplication to the received symbol having the phase rotated to the first quadrant, to thereby generate, by the QPSK likelihood generation, a likelihood for the bit representing whether the received symbol is on the inner circle or the outer circle of the symbol set modulated by the 8QAM modulation scheme.