A rectifying device comprising: a power factor correction circuit comprising an inductor and a first switching element provided to correspond to the inductor, a detection means for detecting a period during which an input power supply voltage is not less than a previously set threshold value; wherein the detection means includes: a photo coupler configured to operate when an absolute value of the input power supply voltage is not less than the previously set threshold value, a second switching element configured to be rendered conductive while an output of the photo coupler is high, an input unit configured so that a low signal is input while the second switching element is rendered conductive and to which a high signal is input while the second switching element is disconnected, and a time measurement unit (IN_1) configured to measure a period during which the low signal is being continuously input in the input unit, a determination means for determining an abnormality in accordance with whether a detection time detected by the detection means is shorter than a previously set normal range, wherein said normal range is set depending on a frequency of an input power supply, a characteristic of the photocoupler, and an allowable error; and a stopping means for stopping an operation of the power factor correction circuit when the detection time is out of the normal range. a power factor correction circuit comprising an inductor and a first switching element provided to correspond to the inductor, a detection means for detecting a period during which an input power supply voltage is not less than a previously set threshold value; wherein the detection means includes: a photo coupler configured to operate when an absolute value of the input power supply voltage is not less than the previously set threshold value, a second switching element configured to be rendered conductive while an output of the photo coupler is high, an input unit configured so that a low signal is input while the second switching element is rendered conductive and to which a high signal is input while the second switching element is disconnected, and a time measurement unit (IN_1) configured to measure a period during which the low signal is being continuously input in the input unit, a determination means for determining an abnormality in accordance with whether a detection time detected by the detection means is shorter than a previously set normal range, wherein said normal range is set depending on a frequency of an input power supply, a characteristic of the photocoupler, and an allowable error; and a stopping means for stopping an operation of the power factor correction circuit when the detection time is out of the normal range. a photo coupler configured to operate when an absolute value of the input power supply voltage is not less than the previously set threshold value, a second switching element configured to be rendered conductive while an output of the photo coupler is high, an input unit configured so that a low signal is input while the second switching element is rendered conductive and to which a high signal is input while the second switching element is disconnected, and a time measurement unit (IN_1) configured to measure a period during which the low signal is being continuously input in the input unit, a determination means for determining an abnormality in accordance with whether a detection time detected by the detection means is shorter than a previously set normal range, wherein said normal range is set depending on a frequency of an input power supply, a characteristic of the photocoupler, and an allowable error; and a stopping means for stopping an operation of the power factor correction circuit when the detection time is out of the normal range.