A semiconductor integrated circuit device includes a target circuit of a low power consumption mode having at least one flip-flop circuit to which a clock signal is supplied in a normal operation mode and in a low power consumption mode, and a logic circuit to which each output of the at least one flip-flop circuit is input, wherein each of the flip-flop circuits includes a selector that selects a normal data signal in the normal operation mode, selects an inverted output of the flip-flop circuit in the low power consumption mode, based on an operation-mode switching signal that designates switching between the normal operation mode and the low power consumption mode, and inputs the selected signal to a data input terminal of the flip-flop circuit.