A resonant power conversion apparatus and a controlling method of the resonant power conversion apparatus are provided. The resonant power conversion apparatus includes a switch-based resonant converter and a controller. The switch-based resonant converter is configured to supply power to a load. The controller is coupled to the switch-based resonant converter and the load and configured to control switching of the switch-based resonant converter to regulate power conversion of the switch-based resonant converter. The controller has a voltage control loop and a current control loop. The controller detects a driving state of the load and enables one of the voltage control loop and the current control loop according to the detection result to adjust a switching frequency of the switch-based resonant converter.