There is provided switching power unit comprising: a PFC voltage detector that detects PFC voltages of the power-factor improvement unit; an output voltage detector that is provided in a current resonance converter unit; a switching controller into which output signals from the PFC voltage detector and output signals from the output voltage detector are input, wherein the switching controller in a full-bridge circuit of first to fourth switching elements, based on output signals from the PFC voltage detector and the output voltage detector, controls the PFC voltages by changing on-duty of the first and second switching elements, and also controls the output voltages by changing switching frequencies of the full-bridge circuit.