A ring oscillator includes a plurality of ring-connected delay circuits. At least one of the plurality of delay circuits has an SRAM cell and a path circuit connected in parallel to the SRAM cell. The SRAM cell outputs an output signal from a second node to the delay circuit in the next stage within the plurality of delay circuits in response to one of rise transition and fall transition of a signal to be input to a first node from the delay circuit in the previous stage within the plurality of delay circuits. The path circuit outputs an output signal to the delay circuit in the next stage in response to the other transition of the one of transitions.