In the present invention, a deformation process is applied to a part of an image fiber, and when implementing improvement of the quality of the transmitted image, the improvement of the image quality in the center region and peripheral region of the image fiber in the radial direction is carried out to an equal degree, and a uniform improvement of the entire screen can be carried out. A processed part is formed having a deformation of all cores that is substantially identical by deforming in the radial direction or by deforming and twisting a part of an image fiber having a plurality of cores that function as pixels in the radial direction thereof. The image fiber can be manufactured by a processing in which by a part of the image fiber having a plurality of cores that function as pixels is heated, and deformed in the radial direction thereof or simultaneously deformed and twisted in the radial direction thereof this heated part.