To provide a decontamination device for radioactive dusts for mechanically separating radioactive dusts caught by a filtration element, floating them, collecting them, and decontaminating the filtration element.

The decontamination device for radioactive dusts is provided with a decontamination chamber 1 for storing a contaminated filtration element E and a carrier device 4 for putting in and out the filtration element E. Inside the decontamination chamber 1, a separation device 5 for separating and floating the radioactive dusts caught by the filtration element E is installed. The radioactive dusts floating inside the decontamination chamber 1 are collected by a collection device 6 and filtered. The separation device 5 comprises a striking member 20 for beating the filtration element E and an air nozzle 21 for jetting pressured air to the filtration element. The filtration element E is beaten by the striking element 20, the radioactive dusts are separated from the filtration element E, the separated radioactive dusts are floated by the air nozzle 21, and they are collected by the dust collection device 6.