A support unit for supporting an OPM holder so as to be perpendicular to a laser beam axis is disposed in the lower part of the OPM holder. A rotary shaft is inserted into the support unit and rotary shaft support unit, and the OPM holder and DT base are assembled together. Thus, a rotation support unit is composed. The rotation support unit has a degree of freedom in the rotating direction. On the other hand, in the lower part of an RM holder, a support bar is provided. At the DT base, a rotating element and a rotating element support unit supporting the rotating element are composed so as to support the support bar. Thus, a slider structure slidable in the optical axis direction is formed.