In the paper, the biological shielding at the output of the ultracold neutron (UCN) supersource for the WWR-M reactor based on superfluid helium has been designed. The configuration of a casemate, i.e., a biological protection around the thermal column splitter, was calculated. The flux density, the spectrum and the angular divergence of the neutron beam at the exit of the intercanal part of the UCN source, as well as the materials’ geometry and composition inside the casemate were taken into account. The total thickness of the shielding made from steel, polyethylene and lead varied from 85 to 92 cm. The calculated maximum dose rate for neutrons and gammas on the casemate surface did not exceed 1 mrem p.h. Thus, the casemate design of the UCN supersource ensures the safe operation of the facility. The calculation was carried out by the Monte Carlo method within the SCALE-6.2 complex using the MAVRIC program.