An obstacle-detectable mobile robotic device includes a frame body capable of traveling on a surface, a control circuit mounted to the frame body for controlling the traveling manner and direction of the frame body, and a detection system mounted to the frame body and electrically connected with the control circuit. The detection system has an optical emitter, an optical receiver, and a reflector. The optical emitter emits the light onto the surface, and the light is reflected onto the reflector and then to the optical receiver to be received by the optical receiver. A receiving area generated by the optical receiver on the reflector never overlaps the surface. Accordingly, the obstacle-detectable mobile robotic device can effectively avoid ambient light pollution to have preferable detection potency.