AIRTIGHT WINDOW

The present invention relates to an airtight window, which can provide a space for enabling the window to be tilted during the fitting thereof into a window frame, and which cuts off the communication between an indoor area and an outdoor area so as to increase thermal insulation and prevent noise when installed. More particularly, an upper frame of a window frame has a square C-shape with an open bottom, and has an installation end tightly contacting an installation part of a building and bent ends which extend downwardly from both ends of the installation end and which are bent inwardly so as to face each other. A movable frame of the window frame also has a square C-shape with an open bottom, and both ends thereof are formed into stopper ends so as to be disposed on and caught at the bent ends of the upper frame. The movable frame has a plurality of rails arranged at the lower surface of a main body of the movable frame interconnecting the stopper ends. The movable frame is slidable in the vertical direction within the upper frame, such that the upper end of the window can be fitted into the upper frame and the lower end of the window can be fitted into a lower frame of the window frame when the window is installed in the window frame, thereby enabling the easy installation of the window in the window frame.