PROBLEM TO BE SOLVED: To carry out lifting operation with ease.SOLUTION: A cask 11 includes: a trunk which forms a cylindrical shape with an opening formed on one side and a bottom formed on the other side, and is capable of storing radioactive materials on the inside; a lid part 13 which can be detachably attached to the trunk so as to block the opening; and a plurality of trunnions 41 which are disposed so as to project outward from predetermined positions of the trunk, and each of whose peripheral surface part is constituted as a hook part which can be hung and fixed on a laterally installed frame, and each of which has a lock hole in a projection end part. In order to transport the cask 11, the following steps are included: hooking a first suspension part 52 on the hook part of the trunnion 41 in a state that the cask 11 is raised in the water of a pool 61 with the lid part 13 facing upward, in order to lift and take out the cask 11 from the pool 61; and inserting a second suspension part into the lock ho
