A power supplying device performs both of a suppression of EMI noise and a reduction in an output voltage. In the power supply device, a switching control device that controls a switching element according to a pulse control signal includes a PPM circuit that modulates a pulse position; a PWM circuit that modulates a pulse width; and a pulse generator circuit that generates a pulse modulated by the PPM circuit and the PWM circuit. When a pulse interval of the pulse modulated in the pulse position by the PPM circuit is sparser than the pulse interval of the pulse before the modulation, the PWM circuit lengthens the pulse width. On the contrary, when the pulse interval of the pulse modulated in the pulse position by the PPM circuit is denser than the pulse interval of the pulse before the modulation, the PWM circuit shortens the pulse width.