A charging device comprising: a converter portion configured to output a charging voltage to a charging subject; and a control portion (5 configured to output a control signal having a pulse width determined based on a value of the charging voltage to a switching element in the converter portion, thereby rendering the switching element in an on-state for a time period corresponding to the pulse width, characterised in that the control portion is configured to change an interval at which to output the control signal in accordance with the value of the charging voltage, thereby lengthening the output interval of the control signal as the value of the charging voltage decreases, wherein the control portion is configured to regularly omit the control signal which is otherwise kept outputted at predetermined intervals, thereby lengthening the output interval of the control signal that is actually outputted, wherein the control portion includes: a storage portion having count defaults stored therein in correlation with values of the charging voltage; a pulse width determination portion configured to determine a pulse width of the control signal on the basis of a value of the charging voltage and a count default stored in the storage portion; and a control signal output portion configured to count down a count value from the count default to zero and configured to output the control signal with the pulse width determined by the pulse width determination portion, and the count default to be read from the storage portion is configured to increase as the value of the charging voltage decreases. a converter portion configured to output a charging voltage to a charging subject; and a control portion (5 configured to output a control signal having a pulse width determined based on a value of the charging voltage to a switching element in the converter portion, thereby rendering the switching element in an on-state for a time period corresponding to the pulse width, characterised in that the control portion is configured to change an interval at which to output the control signal in accordance with the value of the charging voltage, thereby lengthening the output interval of the control signal as the value of the charging voltage decreases, wherein the control portion is configured to regularly omit the control signal which is otherwise kept outputted at predetermined intervals, thereby lengthening the output interval of the control signal that is actually outputted, wherein the control portion includes: a storage portion having count defaults stored therein in correlation with values of the charging voltage; a pulse width determination portion configured to determine a pulse width of the control signal on the basis of a value of the charging voltage and a count default stored in the storage portion; and a control signal output portion configured to count down a count value from the count default to zero and configured to output the control signal with the pulse width determined by the pulse width determination portion, and a storage portion having count defaults stored therein in correlation with values of the charging voltage; a pulse width determination portion configured to determine a pulse width of the control signal on the basis of a value of the charging voltage and a count default stored in the storage portion; and a control signal output portion configured to count down a count value from the count default to zero and configured to output the control signal with the pulse width determined by the pulse width determination portion, and the count default to be read from the storage portion is configured to increase as the value of the charging voltage decreases.