A logic circuit is provided which can hold a switching state of the logic circuit even when a power supply potential is not supplied, has short start-up time of a logic block after the power is supplied, can operate with low power consumption, and can easily switch between a NAND circuit and a NOR circuit. Switching between a NAND circuit and a NOR circuit is achieved by switching a charge holding state at a node through a transistor including an oxide semiconductor. With the use of an oxide semiconductor material which is a wide bandgap semiconductor for the transistor, the off-state current of the transistor can be sufficiently reduced; thus, the state of charge held at the node can be non-volatile.