PURPOSE: To sufficiently decompose a resin material to be processed with no nucelide such as cesium accompanying and with the use of a relative small size device.

CONSTITUTION: A device for a resin material to be processed, which oxidizes and decomposes a resin material P to be processed to which radioactive substance sticks, and discharges generated decomposed gas containing no radioactive substance, outside of the system, incorporates an oxidizing and decomposing tank 2 into which the resin material P to be processed is charged, an oxygen bomb 3 for feeding oxidized gas into the tank 2, a vacuum pump 4 for maintaining a predetermined low pressure in the tank 2, and for discharging decomposed gas generated in the tank 2, outside of the system. A high frequency coil 5 applies high frequency waves to an oxidized gas stream introduced into the tank 2, and an agitating blade 6 agitates the charged resin material P to be processed.