A forward-based power conversion apparatus is provided. When the forward-based power conversion apparatus supplies a plurality of (at least two of) output voltages to a load, a reverse voltage, corresponding to a lower output voltage, of a secondary winding of a transformer is captured through an equipped output auxiliary unit, so as to assist an output of a higher output voltage. Accordingly, compared to that described in the related art, the reverse voltage of the secondary winding of the transformer described herein can be converted into an effective power output, so that overall power loss of the power conversion apparatus can be reduced, and conversion efficiency of the power conversion apparatus can be improved.