PURPOSE: To make discrimination close to optimum one possible with a simple circuit constitution for not only a linear transmission line but also a transmission line having a non-linear transmission characteristic by using temporary decision.

CONSTITUTION: The signal from input terminal 100 is inputted to delay line 3 with tap, temporary decision means 9 consisting of sampler 1 and comparator 2, and reliability decision means 12. Data decided temporarily is inputted to shift register-type memory circuit 4 which functions as a pattern estimation means. A desired receiving signal memory circuit is provided with memory circuits 51 and 52 according to 0 and 1 of the symbol to be decided. All outputs of circuit 51 are inputted to switching circuit 131 together with the output of desired receiving signal representative value memory circuit 141 provided separately, and the output of circuit 51 or the output of circuit 141 is selected according to the output of each register of decision means 12 and is inputted to vector distance calculation circuit 61. The same operation is performed for circuit 52.