A secondary battery pack comprising: a cell assembly comprising a plurality of secondary batteries; a pack case having an internal space for accommodating the cell assembly and comprising a terminal cover mounting part having a square-shaped upper surface and four corners, at least one of which is depressed; an electrode terminal connected to the cell assembly and protruding to an outside of the pack case and located on the terminal cover mounting part that comprising a through hole provided in a vertical direction so that the electrode terminal protrudes to the outside; and a terminal cover configured to cover an upper portion and partial side surfaces of the electrode terminal, and to be detachable from the pack case by including a hooking protrusion that is hook-coupled to and released from a stopper that is provided in the pack case, and coupled to the terminal cover mounting part, wherein the terminal cover further comprises a jig hole configured to allow a cover separating jig to be inserted from outside to inside, and the hooking protrusion is provided at an internal area of the terminal cover to be released from the stopper when the cover separating jig inserted through the jig hole pushes the hooking protrusion and an upper plate covering an upper portion of the electrode terminal and side plates partially covering side surfaces of the electrode terminal, and wherein the terminal cover comprises a concave portion formed by depressing a corner where the two side plates cross each other into an internal area of the terminal cover, and the terminal cover mounting part comprises an internal column located at an internal area of the terminal cover based on the concave portion to support the upper plate of the terminal cover, and an external column provided to be inserted in the concave portion in a longitudinal direction from an outer part of the terminal cover. a cell assembly comprising a plurality of secondary batteries; a pack case having an internal space for accommodating the cell assembly and comprising a terminal cover mounting part having a square-shaped upper surface and four corners, at least one of which is depressed; an electrode terminal connected to the cell assembly and protruding to an outside of the pack case and located on the terminal cover mounting part that comprising a through hole provided in a vertical direction so that the electrode terminal protrudes to the outside; and a terminal cover configured to cover an upper portion and partial side surfaces of the electrode terminal, and to be detachable from the pack case by including a hooking protrusion that is hook-coupled to and released from a stopper that is provided in the pack case, and coupled to the terminal cover mounting part, wherein the terminal cover further comprises a jig hole configured to allow a cover separating jig to be inserted from outside to inside, and the hooking protrusion is provided at an internal area of the terminal cover to be released from the stopper when the cover separating jig inserted through the jig hole pushes the hooking protrusion and an upper plate covering an upper portion of the electrode terminal and side plates partially covering side surfaces of the electrode terminal, and wherein the terminal cover comprises a concave portion formed by depressing a corner where the two side plates cross each other into an internal area of the terminal cover, and the terminal cover mounting part comprises an internal column located at an internal area of the terminal cover based on the concave portion to support the upper plate of the terminal cover, and an external column provided to be inserted in the concave portion in a longitudinal direction from an outer part of the terminal cover.