For a routine cleaning and a primary decontamination of tritiated contaminants in the case of decommissioning, a decontamination robot based on dry method utilizing ozone gas treatment was developed. The robot sized of 720(W)x850(D)x1,050(H) mm with a remote and automatic system consists mainly of 5 different part, a flat decontamination port of about 1,000 cm2 for ozone gas exposure with a heater and surrounding rubber curtain to isolate the inside circumstance, an ozone gas generator utilizing creeping discharge method, a gas cooler for the hot air containing tritiated vapor to be trapped, an adsorption vessel packing molecular-sieves for tritium trap, and a circulation pump. The amount of suction air is larger than that of the exposure air, therefore, non of the contaminants are scattered out from the adsorption port, and this is one of the main characteristic of the robot.