A base structure of a retainer for a shelving comprising operation section supporters (2) which have plural locking sections (5) formed at prescribed intervals on flat surfaces of a flat and vertically long board-like material and a pair of shelf board supporting members (3) which are in engagement with the operation section supporters (2), slidable in the vertical direction and provided with movable locking pieces (11) removably engaged with the locking sections (5) of the operation section supporters (2), wherein the movable locking pieces 11 are automatically engaged with or removed from the locking sections (5).