According to one embodiment, a multiphase circuit, a flip-flop, and a decoder are provided. The multiphase circuit generates multiphase signals of which phases are different from each other by 180/M degrees by dividing a differential oscillation signal by M (M is an integral number not smaller than 2). The flip-flop captures the multiphase signal in synchronization with an input of a reference signal. The decoder decodes an output signal of the flip-flop.