In a dynamic flip-flop circuit with a data selection function, for example, when data having an H value is selected using a selection signal, a first node N1 is L, a second node N2 of a second dynamic circuit is H, so that an output signal has an H level. In this case, when none of a plurality of pieces of data is selected using a selection signal, the first node N1 is H, so that the electric charge of the second node N2 is discharged and the output signal erroneously has an L level. However, in this case, an output node N3 is H and a fourth node N4 is L, so that an n-type transistor of the second dynamic circuit is turned OFF, thereby preventing the second node N2 from being discharged. Therefore, a normal operation is performed while securing a satisfactorily high-speed operation even when none of the pieces of data is selected.