Abstract: A slim double-skin structure according to one aspect of the present invention may comprise: a window frame, an outer window sash frame provided on an outdoor side and coupled to the window frame, an outer glass provided on the outer window sash frame, an inner window sash frame provided on an indoor side and coupled to the window frame, an inner glass provided on the inner window sash frame, an awning film provided in a hollow layer formed between the outer glass and the inner glass to serve as a shading, and a case-type glass fixing frame which is provided in the outer window sash frame so as to be located in the hollow layer and fixes the outer glass to the outer window sash frame concurrently with building-in and guiding the awning film.