Disclosed is an apparatus for decreasing a thrust of a radial flow turbine. The apparatus includes a rotary shaft having an axial through-hole in the interior thereof, a rotor assembled in the rotary shaft and having a rotor hub and rotor blades formed on an outer peripheral surface thereof, a casing configured to isolate the rotary shaft and the rotor from the outside, and a shaft seal configured to maintain a seal between the rotary shaft and the casing.