An embodiment connecting system includes a branch connector connected to a battery and configured to branch a high voltage, a first interlock circuit within the branch connector configured to form a closed circuit by being connected to a second interlock circuit within a load connector when the load connector that transfers the branched high voltage to a load is connected to the branch connector, a transmitting antenna transmitting a radio wave when the closed circuit is formed, and a controller identifying the branch connector based on a resonance frequency of the radio wave and determining whether a connection defect occurs in the identified branch connector based on an electric field strength of the radio wave, wherein the resonance frequency corresponds to a conductor pattern formed at a predetermined position of the transmitting antenna.