Disclosed is an overcurrent protection apparatus in a switching power supply, including a power switching element for interrupting the primary current of a transformer, and a control circuit for generating control pulses which are modulated in pulse width in accordance with a variation in the rectified output voltage on the secondary side of the transformer, the opening and closing of the power switching element being controlled by the control pulses to maintain the rectified output voltage at a constant value. The overcurrent protection apparatus further includes overcurrent detection means which issues an overcurrent detection signal after detecting that a current flowing into the power switching element has exceeded a prescribed value; memory means set by the overcurrent signal; a gate circuit for blocking the passage of control pulses when the memory means has been set; and reset means for resetting the memory means in response to the trailing edge of a control pulse. The switching of the power switching element is controlled by the memory means so that the power switching element is turned off when the memory means has been set, and turned on when the memory means has been reset.