The invention relates to a ladder chair for a bookshelf. The ladder chair for the bookshelf comprises two parallel supports arranged obliquely and an adjusting frame. The middles of the two supports are connected through a limiting rod, the lower ends of the supports are fixedly connected through a horizontal footboard, a fixing supporting foot arranged obliquely relative to the corresponding support is arranged downwards on each support, and a boss is arranged on the part, above the limiting rod, of the inner side of each support. The outer end face of the footboard is obliquely arranged and is parallel to the supports, and rotating supporting feet capable of rotating outwards are arranged on the two sides of the outer end of the footboard respectively, wherein the back faces of the rotating supporting feet can coincide with the outer end face of the footboard. One end of the adjusting frame is rotationally arranged at the upper ends of the rotating supporting feet, and a concave arc is arranged at the other end of the adjusting frame. The concave arc can be arranged at the inner end of the footboard or the bosses in a sleeving mode. The ladder chair can be used as a chair and can also be used as a ladder; furthermore, when the ladder chair is used as the ladder, the height of the chair can be increased so that people can sit on the chair conveniently to tidy the bookshelf, and higher user-friendly performance is achieved.