The utility model discloses a bed widening device. The widening device comprises a widening board, telescopic bed legs and bed connecting parts, the widening board comprises a part A, a part B, a part C and a part D, the telescopic bed legs are arranged on the part A of the widening board, the bed connecting parts are arranged on the part D of the widening board and arranged on the side edge of the part D of the widening board, and the widening board comprises hinges a, clamping pieces and clamping nails. The part B and the part C of the widening board are connected through the hinges a, and the clamping pieces and the clamping nails are arranged between the corresponding positions of the edge of the widening board. The clamping pieces and the corresponding clamping nails can be just stably buckled. The telescopic bed legs comprise rotary shafts, hollow tubes, insertion pins and adjustable sections. Each rotary shaft is arranged in a rotary shaft fixing frame, the hollow tubes are arranged inside the rotary shaft fixing frames, can rotate around the rotary shafts and are provided with insertion pin positioning holes, multiple insertion holes are formed in the adjustable sections, and the insertion pins are matched with the insertion holes in size. The bed connecting parts comprise movable side plates and hinges b, wherein the movable side plates are connected with the part D of the widening board through the hinges b in a rotating mode.