A focusing position detecting device in which a laser beam is directed through an objective lens toward the surface of an object to form a minute spot on the surface of the object, and the beam reflected from the surface of the object is led through the objective lens again toward a concentrating point, so as to detect the focusing position of the objective lens by measuring the position of the concentrating point. In the device, a photoelectric element is provided to detect the intensity of the reflected beam, and the intensity of the laser beam is so controlled that the output of the photoelectric element is maintained constant.