A semiconductor device includes: a clock synchronizing circuit that operates in synchronization with a clock; an enable signal generating circuit that generates an enable signal in an operation period during which the clock synchronizing circuit is operated; and a clock supplying circuit that supplies a clock to the clock synchronizing circuit or stop the supply of the clock according to the enable signal when a clock frequency is equal to or lower than a predetermined frequency, and supply a clock to the clock synchronizing circuit, irrespective of the enable signal, when the clock frequency is higher than the predetermined frequency.