PURPOSE: To provide a robot capable of automatically applying blast treatment and metalikon treatment over the entire inner surface of work such as tank.

CONSTITUTION: When control system is set into operatin, actuator 4 is expanded and component parts of a robot located upwardly of frame 3 are put into tank T from opening Ta. Then, actuators 4, 7, 10, 13, 16 are controlled elaborately, such that nozzle 17 is moved to every portion along the inner surface of tank T. While doing so, blast material is ejected from the nozzle 17 to apply blast treatment on the inner surface of tank T. In the above arrangement, arms 5, 8 and members 11, 14 are designed to be freely movable in work T