Provided is a functional fabric including a base fabric layer; and an insulation flexible sheet attached to at least one surface of the base fabric layer. The insulation flexible sheet includes a first flexible base; and an insulation coating layer attached to at least one surface of the base. The insulation flexible sheet may additionally include a second flexible base on the insulation coating layer. Accordingly, the functional fabric may have effective insulation properties by using silica particles having pores in a small amount used, and may have excellent strength due to the strength of the silica particles. In addition, Manufacturing methods of an insulation flexible sheet and a functional fabric are provided.