An oversampling time-to-digital converter includes an input pulse generation circuit generating two pulse signals, a reference pulse generation circuit generating two pulse signals, a swap circuit swapping two pulse signals, a multiplexer selecting an output of the input pulse generation circuit or the swap circuit, a time-to-current conversion circuit outputting two pulse currents in accordance with an output of the multiplexer, a current mirror circuit whose input and output terminals receive the two pulse currents, an integration circuit integrating a differential current between the pulse current connected to the output terminal of the current mirror circuit and an output current of the current mirror circuit, and a comparison circuit comparing an output signal of the integration circuit to a threshold voltage. An output signal of the comparison circuit is given to the swap circuit as a control signal.