A Q switch resonator includes: an optical resonator comprising at least two mirrors, and configured to accumulate power of a continuous wave or an intermittent continuous wave incident from an outside; and a switching element provided in the optical resonator. The switching element is configured such that, when the power accumulated in the optical resonator increases to a predetermined level, the switching element outputs an optical pulse by lowering a Q factor from a first level to a second level lower than the first level.