To make the connecting work of thermally insulating panels easy by enabling the handling of a hook unit with a hexagon wrench through a cylindrical member formed on the wall plate of a panel in the thermally insulating panels connected by latching between pin units and hook units used for a prefabricated refrigerator.

After arranging a protruding frame body 6 attached with a hook unit 8 to the edge part between walls 4 and 5 and holding the hook unit 8 to the wall plate 5 through the cylindrical member 18, the thermally insulating panel 2 is produced filling foamed insulating material 15 between the wall plates 4 and 5. The thermally insulating panel 2 built in with the pin unit 13 is arranged with a recessed frame material 11 attached with the pin unit 13 to the edge part of the walls 4 and 5, and produced by filling the foamed insulating material 15 between the wall plates 4 and 5. Between the insulating panels 2 are connected by latching the hook part with the pin of the pin unit 13 inserting the hexagon wrench through a wrench inserting hole 17 and rotating the rotor of the hook unit 8 while the edges of the insulating panels 2 are touching each other.