Provided is a time-domain voltage comparator including a voltage-time converter. The voltage-time converter includes a conversion unit and an output unit. The conversion unit includes a first MOS transistor which shifts a voltage level of the first detection node according to an external first voltage signal, and a second MOS transistor which shifts a voltage level of the second detection node according to an external second voltage signal. The output unit generates first and second output signals in response to voltages of the first and second detection nodes. The output unit determines a shifted time of the first output signal according to a voltage level of the first detection node and determines a shifted time of the second output signal according to a voltage level of the second detection node.