A robot cleaner includes a body; a driving unit; at least one sensor configured to detect an obstacle; a cleaning unit, the cleaning unit including a brush unit and a fan unit; a dust box to store dust inside of the dust box, the dust box being detachably mounted to the body; and a dust sensing unit including a light emitting unit to transmit light and a light receiving sensor to sense the light transmitted by the light emitting unit, the light emitting unit and the light receiving sensor being fixed on the body and outside of the dust box, and the light emitting unit being configured to transmit light through the inside of the dust box. The driving unit, the at least one sensor, the cleaning unit, the dust box, and the dust sensing unit are positioned on or in the body of the robot cleaner.