A robot mechanism adopts a dry cleaning method to clean the surface of live-line insulators without using water and can perform cleaning and inspection of the surface of the live-line insulators while automatically moving along an insulator string. The robot mechanism includes a main unit having upper and lower wing frames connected with each other by a connecting bracket to surround the insulator string, a cleaning unit disposed between the upper and lower wing frames and including a base frame to perform dry cleaning with a rotational brush and a CM guide, a lift unit including a clamp and a ball-bearing screw to move the main unit up or down, and an inspection unit to electrically inspect the insulators; and a coupling unit to couple a pair of the main units to allow the pair of main units to move along a tension insulator string or a suspension insulator string.