Abstract: The present invention provides a heat insulation covering for a spherical storage tank such as an LNG tank or the like for storing an extremely low temperature liquid. The covering is constructed by using elongated panel-like heat insulating panels. A plurality of slit parts having a U-shaped cross section are formed along the longitudinal direction of a foam-resin heat insulating panel formed in an elongated panel-like configuration. In the slit part, a heat insulating material is inserted. The material has a sufficient expandability under extremely low temperatures. The heat insulating panel can be deformed along the curvature of the surface of the spherical tank. The heat insulation covering of the spherical tank is formed of the heat insulating panels which have an elongated configuration. With such a structure, only a few kinds of heat insulating panels need be prepared, which is favorable in terms of cost.