To provide a space multiplex signal detection circuit capable of obtaining an excellent error rate characteristic by suppressing an increase in the circuit scale if when a modulation multivalued number is particularly increased in the case of receiving a signal subjected to space multiplexing to detect the signal. SOLUTION: A transmission signal candidate narrow-down circuit 108 refers to a proximity signal point data table 109 and stepwise narrows down the number of a plurality of transmission signal candidates to a prescribed number of the candidates. The proximity signal point data table 109 stores the cross-reference between signal points closer on a transmission constellation to signal points of transmission signals of each of transmission systems estimated by a transmission signal estimate circuit 107. A maximum likelihood estimate circuit 113 receives candidates of the transmission signal sequences and metrics corresponding to the candidates and outputs a transmission signal sequence whose metric value is least as a final transmission signal sequence.