The invention relates to a hot stamping die for forming a composite material with a flanging structure. The hot stamping die comprises an upper die body, a middle die body, a lower die body and a die core; the lower die body is fixed to a press platform, the upper die body is fixed to the lower portion of a press pressing plate, the middle die body comprises a sliding block and a sliding block rail seat matched with the sliding block, and the sliding block rail seat is fixed to the upper portion of the lower die body; the die core is fixed to the sliding block rail seat, the die core is of a rectangular structure, and the upper portion and the side face of the die core are provided with the composite material to be subjected to hot stamping; two or more sides in the peripheral direction of the hot stamping die are provided with inclined guide pillars; the upper ends of the inclined guide pillars are fixed into the upper die body; after die closing is conducted, the inclined guide pillars penetrate through corresponding holes in the upper die body, the sliding block, the sliding block rail seat and the lower die body from top to bottom in a mode of being inclined outwards, the upper die body is tightly pressed on to the upper surface of the die core, and the sliding block inwards slides in place under the action of the inclined guide pillars and the upper die body and is correspondingly pressed on the side face of the die core; after die sinking is completed, the upper die body is lifted upwards, the inclined guide pillars are separated out of the hole of the lower die body and drives the sliding block to slide outwards along the sliding block rail seat, and the composite material with the flanging structure is pressed.