In a through hole closing process, a metal plate is attached to one
surface of a conductive base member having a plurality of through holes
by the use of a magnet, in a copper plating process, a copper plating
layer is formed on the conductive base member and the metal plate exposed
within the through holes, from the side of the conductive base member
where the metal plate is not attached, thereby to fill up the through
holes, in a film forming process, a Pd alloy film is formed by plating on
the surface of the conductive base member after removal of the metal
plate, and in a removal process, the copper plating layer is removed by
selective etching, thereby to produce a hydrogen production filter that
is used in a reformer of a fuel cell so as to be capable of stably
producing high purity hydrogen gas.