To provide a motor actuator capable of rotating a driven member at a tip side of a supporting member, and preventing undesired motion of the driven member even when the supporting member itself is oscillated or linearly moved.

In a louver device, a louver supporting member 22 is oscillated or linearly moved. A third stepping motor 80 is disposed at a basic end side of the louver supporting member 22 when a louver 2 is rotated at the tip side of the louver supporting member 22, and a timing belt is hung between a basic end-side pulley 82 and a tip-side pulley 85. Thus the undesired motion of the louver caused by backlash can be prevented, unlike a case applying a gear mechanism.