A semiconductor device capable of stabilizing power supply by suppressing power consumption as much as possible. The semiconductor device of the invention includes a central processing unit having a plurality of units and a control circuit, and an antenna. The control circuit includes a means for outputting, based on a power supply signal including data on power supply from an antenna (through an antenna) or a load signal obtained by an event signal supplied from each of the units, one or more of a first control signal for stopping power supply to one or more of the units, a second control signal for varying a power supply potential supplied to one or more of the units, and a third control signal for stopping supplying a clock signal to one or more of the units.