A switched-mode power supply device that rectifies and smoothes a direct input voltage to obtain a predetermined output voltage is disclosed. A series circuit includes a reactor and a switching element and the circuit switches the direct input voltage. An OFF time calculator calculates an OFF time of the switching element based on the direct input voltage, the output voltage, and an ON time of the switching element calculated based on the output voltage and a reference value. A frequency calculator calculates at least one of a period and a frequency based on the OFF time calculated by the OFF time calculator and the ON time. A controller that controls switching of the switching element based on a result of comparison between one of the period and the frequency, and a corresponding one of a reference period and the reference frequency.