In order to produce a logic circuit excellent in circuit characteristics which are area, delay time and power consumption by combining pass transistor logic circuits and CMOS logic circuits, a binary decision diagram is created from a Boolean function, and respective nodes of the diagram are mapped into 2-inut, 1-output, 1-control input pass transistor selectors to synthesize a pass transistor logic circuit. In the pass transistor logic circuit, a pass transistor selector operating as a NAND or NOR logic with any one of its two inputs excluding the control input being fixed to a logical constant “1” or “0” is replaced with a CMOS gate operating as a NAND or NOR logic logically equivalent to the pass tansistor selector if the value of a predetermined circuit characteristic obtained by the replacement is closer to an optimal value (if the resulting logic circuit is smaller in area, delay time or power consumption than the original pass transistor logic circuit).