The utility model relates to extending and auxiliary devices of forklift arms and provides a forklift extending device which is exquisite in structure, simple and efficient in using method and capable of completing transferring of a large-size coil through a common forklift after being used. A forklift comprises a pair of forklift arms, the extending device comprises a pair of extending arms and a pair of placing rods, the extending arms are provided with root ends and pointed ends, containing grooves matched with the forklift arms are formed in the end faces of the root ends, and thus the extending arms are made to be connected to the forklift arms in a sleeved mode. The placing rods are arranged at the pointed ends and the root ends of the extending arms respectively, and the placing arms are perpendicular to the extending arms and are detachably connected to the top faces of the extending arms. The forklift extending device has the advantages of being exquisite in structure and simple and efficient in using method.