A robot cleaner includes a main body, a traveling unit installed in the main body, to move the main body, an ultrasonic sensor to emit an oscillation wave, to receive a reflection wave reflected from an object surface, and to output vibration generated by the oscillation wave and vibration generated by the reception of the reflection wave as an electrical signal, a waveform analyzer to calculate a generation time period of the electrical signal output from the ultrasonic sensor, and a controller to determine information about the object surface based on the calculated generation time period of the electrical signal, and to control movement of the traveling unit based on the information about the object surface.