An aspect of the present invention is directed to a method for forming a mirror-reflecting film on a
waveguide in an optical wiring board, characterized in that a multilayer film, in which a base, a
metal layer and an
adhesive layer are layered in this order, is used, and the
metal layer is transferred and bonded to an inclined face for mirror-reflecting film formation provided on the
waveguide, with the
adhesive layer of the multilayer film intervening. The present invention provides a method which, when forming a mirror-reflecting film on a
waveguide in an optical wiring board, enables inexpensive and easy formation of the mirror-reflecting film, using the smallest quantity of
metal possible and employing comparatively simple facilities and techniques.