The invention belongs to the technical field of machinery and discloses a novel angle steel flattening device which comprises an upper die plate and a lower die plate. A T-shaped mounting groove is formed below the upper die plate. A sliding plate is inserted into the mounting groove in a penetrating mode. A spring is arranged between the bottom of the sliding plate and the upper die plate. The inner side and the outer side of the lower die plate are welded with fixing rings respectively. The outer side fixing ring is fixedly provided with a forming die through an inserting rod. A horizontal gap is formed between the forming die and the lower die plate. The inner side fixing ring is fixedly provided with a pre-forming die which is of a square-shaped structure, wherein one angle is inserted into the lower die plate. A pre-forming gap is formed between the side of the pre-forming die and a groove machined in the lower die plate. Forming angle steel obtained through the novel angle steel flattening device is attractive in appearance and stable in quality, during using, operation is easy, forming speed is high, efficiency is high, and the novel angle steel flattening device is ideal.