A semiconductor integrated circuit including: a circuit block having an internal voltage line; an annular rail line forming a closed annular line around the circuit block and supplied with one of a power supply voltage and a reference voltage; and a plurality of switch blocks arranged around the circuit block along the annular rail line, the plurality of switch blocks each including a voltage line segment forming a part of the annular rail line and a switch for controlling connection and disconnection between the voltage line segment and the internal voltage line.