According to one embodiment, a semiconductor device includes: a first scan chain and a second scan chain each including a plurality of cascaded flip-flops; a plurality of power supply lines that supply a power supply voltage to the first and second scan chains, extend in a first direction, and are arranged in a second direction intersecting with the first direction; and a clock control circuit that supplies a first clock to the first scan chain and a second clock to the second scan chain, the second clock having timing different to that of the first clock. The plurality of flip-flops are arranged along the second direction.