The invention discloses a machine door device of an injection molding machine, which solves the problem of machine door clamping stagnation and low opening reliability. The machine door comprises a bracket (3), a guide rail arranged on the bracket, a movable machine door (1), and a fixed machine door (2), wherein the guide rail is L-shaped, a horizontal upper guide rail (10) is provided with an upper roller wheel (13); a horizontal lateral guide rail (9) is provided with a lower roller wheel (20); an upper roller wheel shaft (11) passes through an upper roller wheel bearing (12), and one end of the upper roller wheel shaft (11) is fixedly connected with the movable machine door (1); one end of the upper roller wheel shaft (11) is connected with one end of an oil cylinder lug (4), while the other end of the oil cylinder lug (4) is fixedly connected with an output shaft of an oil cylinder (5); and a lower roller wheel shaft (22) passes through a lower roller wheel bearing (21), and one end of the lower roller wheel shaft (22) is fixedly connected with the movable machine door (1). The machine door device improves the work safety of the injection molding machine.