A semiconductor integrated circuit includes: a circuit block having a first power supply line to which one of a power supply voltage and a reference voltage is applied, an internal voltage line, and a circuit cell connected between the first power supply line and the internal voltage line; and a plurality of switch cells each including two voltage cell lines each connected electrically to the internal voltage line, two power cell lines each connected electrically to a second power supply line to which another of the power supply voltage and the reference voltage is applied, a control cell line electrically connected to a switch control line, and a transistor electrically connected between the internal voltage line and the second power supply line.