The invention relates to a side dumping device for a loading machine. The side dumping device comprises a bracket, a bucket, an oil cylinder, V-shaped limiting blocks and a pin shaft used for connecting the bracket and the bucket. The oil cylinder is connected with the bucket through a universal joint pin. Two sloping panels are obliquely arranged on the rear portion of a bucket wall plate of the bucket. The left side and the right side of the bracket are provided with sealing cavity steel channels penetrating through bracket hinged mounting bases. The bracket is provided with an upper limiting block assembly, and a lower limiting block assembly is installed below the bucket. The upper limiting block assembly and the lower limiting block assembly are installed in a nested mode and are both the V-shaped limiting blocks. The bucket and the bracket are both provided with oil cylinder supports which are connected through one set of hydraulic oil cylinder. The hydraulic oil cylinder can be telescoped to push the bucket to rotate around a pivot, so that leftward or rightward dumping is achieved. The degree of freedom is increased, reliable control is realized, and dumping in three directions is achieved. When the loading machine is located at a narrow and small place, the dumping operations in the forward direction, the left side direction and the right side direction can be performed through the side dumping device in the embodiment of the invention, and the phenomenon that a common dumping device is limited by various special environments is broken through.