A heat pipe with ultra-thin capillary structure (2) comprises a tube body and a capillary structure. The tube body is a hollow and flat. The capillary structure is disposed in the tube body as a thin plate body, and is composed of a first laminating surface laminated to a portion of an inner wall of the tube body, a forming surface opposite to the first laminating surface, and a second laminating surface between the first laminating surface and one side of the forming surface. The second laminating surface is laminated onto the inner wall of the tube body to form a vapor flow channel between the forming surface and the inner wall of the tube body. In which, the forming surface is extended along the length direction of the vapor flow channel and is tapered toward the vapor flow channel, so as to be obliquely crossed between the capillary structure and the vapor flow channel becoming a capillary transmission surface.