A light beam adjusting device performs a process on at least two kinds of light beams in combination. Through this light beam adjusting device, a part of a first light beam is emitted from a first light exit face and another part thereof may be emitted from a second light exit face. Similarly, a part of the second light beam is also emitted from the first light exit face, and another part thereof may be emitted from the second light exit face. In this way, regardless of whether the first light beam is turned on or the second light beam is turned on, the light adjusted by the light beam adjusting device can be simultaneously emitted from the first light exit face and the second light exit face.