A zero crossing point detecting device comprising: a crossing point detecting unit configured to detect a crossing of an alternating current voltage and a predetermined positive voltage (Vth); and a control circuit configured to specify a first detection timing, the first detection timing being a timing at which the crossing point detecting unit detects the crossing when the alternating current voltage is being increased, wherein the zero crossing point detecting device is characterized by the control circuit specifying a second detection timing, the second detection timing being a timing at which the crossing point detecting unit detects the crossing during a predetermined detection period, the predetermined detection period being a period from an end time of a detection stop period to a detection period end time, the end time of the detection stop period being determined on the basis of the first detection timing, the end time of the detection stop period being earlier than when the voltage initially crosses the predetermined positive voltage after the first detection timing with the alternating current voltage being assumed to be an ideal alternating current voltage having a sinusoidal waveform of a single frequency, the detection period end time being earlier than when the voltage initially crosses zero volts after end of the detection stop period, the control circuit subtracting a difference between the first detection timing and the second detection timing from a half cycle (Tp/2) of the alternating current voltage to obtain a value, the control circuit halving the obtained value to calculate a zero crossing point specifying parameter (zc), the control circuit specifying a zero crossing time at which the alternating current voltage crosses zero volts on the basis of either one of the first or second detection timing, the zero crossing point specifying parameter and the cycle of the alternating current voltage, the control circuit controlling, on the basis of the specified zero crossing time, a switching operation of a switching element which is used to rectify the alternating current voltage into a direct current voltage. a crossing point detecting unit configured to detect a crossing of an alternating current voltage and a predetermined positive voltage (Vth); and a control circuit configured to specify a first detection timing, the first detection timing being a timing at which the crossing point detecting unit detects the crossing when the alternating current voltage is being increased, wherein the zero crossing point detecting device is characterized by the control circuit specifying a second detection timing, the second detection timing being a timing at which the crossing point detecting unit detects the crossing during a predetermined detection period, the predetermined detection period being a period from an end time of a detection stop period to a detection period end time, the end time of the detection stop period being determined on the basis of the first detection timing, the end time of the detection stop period being earlier than when the voltage initially crosses the predetermined positive voltage after the first detection timing with the alternating current voltage being assumed to be an ideal alternating current voltage having a sinusoidal waveform of a single frequency, the detection period end time being earlier than when the voltage initially crosses zero volts after end of the detection stop period, the control circuit subtracting a difference between the first detection timing and the second detection timing from a half cycle (Tp/2) of the alternating current voltage to obtain a value, the control circuit halving the obtained value to calculate a zero crossing point specifying parameter (zc), the control circuit specifying a zero crossing time at which the alternating current voltage crosses zero volts on the basis of either one of the first or second detection timing, the zero crossing point specifying parameter and the cycle of the alternating current voltage, the control circuit controlling, on the basis of the specified zero crossing time, a switching operation of a switching element which is used to rectify the alternating current voltage into a direct current voltage.