PURPOSE: To intend firm removal of radioactive substances on a floor surface without any danger to a human body by providing a cover covering spot contaminated floor by the radioactive substances, members of washing equipment, a driving motor, a suction pump and a supplying measures of washing liquid.

CONSTITUTION: The invented device has a tilted handle 25 and whole device is moved to a contaminated floor position by casters 26. Then, when a button 30 is pressed, a vacuum pump 21 sucks air in a cover 1 via a hose 20 and a suction hole 19, to make an inside of cover of negative pressure, and therewith the cover 1 descends against a driving spring 27 and contacts completely to the floor surface. After that, when an operating button 31 is pressed, a detergent valve of a washing tank 17 and a valve of a washing tank 16 open to supply a set amount of washing water to the floor surface. Subsequently, when a driving button is pressed, a driving motor 11 rotates and a washing brush 3 and a wiper 4 revolute as well as the washing brush 3 rotates, too. After washing washing out the radioactive substances on the floor surface in the cover 1, contaminators such as the radioactive substances and contaminated water are sucked through the suction hole 19 and the host 20, and is stored in a contaminator tank 23.