A resonant power conversion apparatus including a transformer-based resonant converter and first and second switch control units is provided. The transformer-based resonant converter includes a primary switch circuit and a secondary output circuit configured to provide an output voltage to a load. The first switch control unit is configured to control an ON/OFF operation of the primary switch circuit in response to a status of the load. The second switch control unit is configured to determine whether to activate or inactivate the first switch control unit. When the status of the load is the light-loading or the no-loading, the first switch control unit intermittently controls the ON/OFF operation of the primary switch circuit, and meanwhile, the first switch control unit is inactivated during the primary switch circuit is disabled, so as to substantially reduce the light-loading or no-loading loss of the resonant power conversion apparatus.