The invention discloses a door opening device. The door opening device comprises a wall body, the wall body is internally provided with a lifting cavity extending left and right, lifting columns in left and right symmetry are fixedly installed between the upper end wall and the lower end wall of the lifting cavity, a passage running through and communicating with the indoor and the outdoor front and back is arranged between the left lifting column and the right lifting column, the wall body is internally provided with first transmission cavities located above the lifting cavity in a left and right symmetry manner, second transmission cavities extending left and right are arranged above the left first transmission cavity and the right first transmission cavity, positions between the secondtransmission cavities and the left and right two first transmission cavities are both rotatably provided with first rotating shafts extending up and down, the upper ends of the first rotating shafts are in rotating fit connection with the upper end walls of the corresponding second transmission cavities, the lower ends of the first rotating shafts are in rotating fit connection with the lower endwalls of the corresponding first transmission cavities, the first transmission cavities are internally provided with first thread winding wheels fixedly installed to the outer surfaces of the corresponding first rotating shafts, and second rotating shafts are rotatably installed between the front end walls and the rear end walls of the corresponding first transmission cavities.