A rotary laser beam emitter includes a base unit including a reference reflector with a reference reflective face parallel to a reference plane, a rotary element rotatably supported on the base unit around a rotary axis, and a beam emitting unit contained in the rotary element and including a light source and an optical emission system emitting the laser beam from the light source in a direction parallel to the reference plane on the optical axis. When the rotary element is inclined relative to the rotary axis and the emitted laser beam is inclined to the reference plane, the optical emission system emits the laser beam from the light source to the reference reflective face and emit the laser beam reflected by the reference reflective face in a direction inclined to the optical axis of the laser beam so as to neutralize the inclined laser beam.