Provided are a wirelessly charged robot cleaner in a robot cleaning system and a controlling method thereof. The wirelessly charged robot may include a target resonator to receive a resonance power through energy-coupling with a source resonator of a wireless power transmitter, a wireless power receiving unit to convert the received resonance power into a rated voltage, and a battery controller to check a remaining capacity of the battery based on a scope of a predetermined area to be cleaned, and to charge, using the rated voltage, the battery based on the remaining capacity of the battery.