A method for producing a printed wiring board and printed wiring board substrate

One embodiment of the present invention provides a substrate for a printed wiring board, comprising: an insulating base film; and a metal layer laminated on at least one surface of the base film. Disposed between the base film and the metal layer with a plurality of fine particles, and said fine particles is formed of a main metal of the metal layer of the same metal or metal compound. Preferably, the average particle diameter of the plurality of fine particles is 20nm or less than 0.1nm. Preferably, the plurality of fine particles is formed of a metal oxide or metal hydroxide. Preferably, the plurality of fine particles present between the base film and the metal layer in a form of a layer. Preferably, the metal layer comprises a metal particles layer formed by firing metal nanoparticles.