A detecting apparatus and method of a robot cleaner is disclosed. The apparatus includes a detecting unit provided with a transmitting unit for sending a signal to detect the floor and a receiving unit for receiving a signal sent from the transmitting unit to be reflected on the floors an optic angle adjusting unit disposed at least one of the transmitting unit and the receiving unit and configured to adjust optic angles of the signals, and a light shielding unit configured to partially shield a signal sent through the optic angle adjusting unit in order to reduce a deviation of each signal of the transmitting unit and the receiving unit. Accordingly, a measurement deviation with respect to color and feel of the floor can be reduced. Also, an amount of light received at the receiving unit can be obtained as much as required, which allows an accurate detection of the detecting apparatus. In addition, even if there are both drop-off and bump on the floor, the robot cleaner can smoothly operate.