Provided is an underground double wall assembly using extruded cement panels. The provided underground double wall assembly comprises: a plurality of extruded cement panels horizontally connected and fixated to a waterproof protrusion and a ceiling with a predetermined interval from an external wall surface of an underground wall; and a plurality of elastic clips to fixate the extruded cement panels to the waterproof protrusion and the ceiling. First and second protrusion parts are formed on both ends of the extruded cement panels. Separation connecting units face and correspond to each other, and have vertical surfaces and inclined surfaces to horizontally connect each extruded cement panel in the first and second protrusion parts. Hollows wherein the elastic clips are installed are formed on the first and second protrusion parts.
