Provided is an oscillation circuit including a first terminal to which a first end of a crystal resonator is to be connected, a second terminal to which a second end of the crystal resonator is to be connected, a first resistor connected between the first terminal and the second terminal, a first transistor that is an N-channel transistor whose source is grounded, whose gate is connected to the first terminal, and whose drain is connected to the second terminal, a second transistor that is a P-channel transistor whose drain is connected to the drain of the first transistor, a third transistor that is a P-channel transistor biased by a constant current. A first state in which the first transistor and the second transistor operate as an inverter circuit, and a second state in which the second transistor and the third transistor operate as a current mirror circuit are switchable.