This utility model discloses a flat-mounted, concealed-sash, slim, heat-insulating window, belonging to the technical field of heat-insulating windows. It includes a window frame and a window sash. The window frame includes an outer frame and an inner frame, connected by two parallel first
thermal insulation strips. The window sash includes an outer sash and an inner sash, connected by a multi-cavity
thermal insulation strip. A double-glazed pane is installed between the outer and inner sashes. A first
sealant is installed between the outer and inner sashes, with an extended
sealant attached to the back of the outer sash. The outer frame includes an extended edge plate extending towards one side of the window sash, flush with the extended
sealant. The inner sash includes an extended edge plate extending towards one side of the window frame, flush with the inner frame. This utility model achieves an extremely slim and stable window frame and sash structure, with a flush
visible surface, resulting in a simple and aesthetically pleasing overall appearance and excellent visual appeal, while reducing safety hazards caused by uneven structures.