A remote-controlled actuator assembly includes a distal end member fitted to a tip end of a spindle guide section (3) for alteration in attitude, a tool rotatably provided in the distal end member, a tool rotation drive source (41) for rotating the tool, and an attitude altering drive source (42) for operating the attitude of the distal end member. The spindle guide section (3) has a rotary shaft (22) for transmitting a rotation of the tool rotation drive source (41) to the spindle and an attitude altering member (31) to alter the attitude of the distal end member. The attitude altering drive source (42) includes a reduction unit (43) to reduce a speed of input rotation from the attitude altering drive source (42), a motion converter mechanism (44A) to convert a rotational output from the reduction unit (43) to advance/retraction motion, and an output member to cause the attitude altering member (31) to advance/retract according to an output of the motion converter mechanism (44A).
