PURPOSE: To provide a protective device easy to manufacture, low in cost and strong against impact and stress by providing a metal cup integral with a sleeve thread-fastened to each shoe part of a tank, and a lock nut thread-fastened to a washer of truncated cone shape made of elastic material.

CONSTITUTION: Each end of a tank is protected by a means having a metal cup 22, a washer 23 made of elastic material, and a nut 24 arranged at each shoe part. The metal cup 22 is integral with a sleeve 22a threaded inside, and thread-fastened to a thread 25 cut on the outside of an axial tenon of the corresponding shoe part. The cup 22 is of truncated cone shape with the same cone as a support face 13 of the shoe part. The washer 23 is of truncated cone shape formed of rubber or other elastic and compressible material, and absorbs the fastening torque of the cup 22 and most of impact or stress applied to the cup 22 to protect an outside shell 4 of the tank. A lock nut 24 maintains the cup 22 completely in an appropriate place while avoiding thread looseness.