A switching power supply circuit including a phase angle detector circuit detecting a phase angle specified in advance based on a peak hold signal, a continuous conduction control setting circuit holding a voltage value corresponding to a peak current value of an inductor current detection voltage in every switching cycle and during a one-shot pulse when the peak is held and outputting a signal at the point of detection to determine to enable or disable a second set pulse set by the continuous conduction control setting circuit. When the second set pulse is disabled, a selector circuit carries out control using critical conduction control to turn on a switching element using a ZCD comparator detecting that the inductor current has reached zero, because of which the peak current does not increase.