A laser beam emitting apparatus includes a semiconductor laser, a photodiode for detecting the intensity of the laser beam, an amplifier for amplifying the detection signal from the photodiode, and a variable resistor connected to the amplifier for adjusting the gain of the amplifier. In one embodiment, these elements are provided in a unit structure so that the adjustment of the gain of the amplifier can be carried out in advance. In another embodiment, a collimating lens for collimating the laser beam emitted from the laser is also provided in the same unit. In another embodiment, a single-piece support is provided to support the semiconductor laser, the collimating lens, and an aperture plate formed with an aperture for shaping the collimated laser beam. As a modification, the single-piece support can be made dual in structure while maintaining the structural integrity of the support.