<p>A mirror surface angle adjuster in which an assembling error of a first housing (A1) and a second housing (A2) affecting less the assembling accuracy of a worm wheel (A71) and in which assembling work can be carried out easily and quickly. The mirror surface angle adjuster is characterized in that the worm wheel (A71) built-in in an actuator (A) is held in the second housing (A2) such that it cannot coming out in the direction of its central axis but can pivot freely about the central axis. Assembling work of the mirror surface angle adjuster can be carried out easily and quickly, and even if an error arises in assembling the first housing (A1) and the second housing (A2), assembling accuracy of the worm wheel (A71) is less affected.</p>
