The utility model relates to a supporting device of a shearing machine, which is characterized by comprising a cylinder support (1), a cylinder connecting pin (2), a cylinder (3), a supporting rack support (4), a support pin (5), a cylinder piston rod pin (6), a supporting rack (7) and a supporting roller component (8), the cylinder support (1) is arranged on the shearing machine (A), the cylinder (3) is disposed on the cylinder support (1) through the cylinder connecting pin (2), a piston rod end of the cylinder (3) is connected with the supporting rack (7) through the cylinder piston rod pin (6), the supporting rack support (4) is disposed on the shearing machine (A), the supporting rack (7) is arranged on the supporting rack support (4) through the support pin (5), and the supporting roller component (8) is arranged on the supporting rack (7). When the shearing machine shears the final stage of a material during a cutting-to-length process, the supporting device can prevent the material dropping and guarantees that the length of the final stage of the material can not exceed set size, thereby increasing processing quality and enhancing use ratio of equipment.