Abstract: Proposed is a fixing device for use to handle a spent nuclear fuel assembly and a method for installing same, capable of improving structural reliability of the spent nuclear fuel assembly, the fixing device including: a housing (100) provided with a plurality of free end portions (110), stopper protrusions (120), a first male thread (131), and a female thread (132); a rod member (200) having a length longer than the housing (100), the rod member being provided at a tip end thereof with a pressurization protrusion (210) having an outer diameter larger than an inner diameter of the free end portions, and provided with a second male thread screw-assembled with the female thread (132), thereby being screw-assembled with the housing (100); and fixing members (310 and 320) to fix the housing (100) to the nuclear fuel assembly by being screw-assembled with the first male thread of the housing (100).