A three dimensional printing apparatus including a carrying plate, a transparent plate, an elastic film, and a bump is provided. The transparent plate is disposed on the carrying plate. The elastic film is disposed on the transparent plate. The bump is disposed between the elastic film and the carrying plate. An interface between the transparent plate and the elastic film is in communication with an external space through a fluid channel between each bump and the elastic film. An orthographic projection area of the bump on the transparent plate is not more than ¼ of a surface area of the transparent plate.