For the purpose of achieving enhanced reliability with respect to interlayer connections of printed wiring boards, a manufacturing method of printed wiring boards of the present invention includes any one of the steps of A) restricting the resin flowing in hot press processing, B) joining fiber reinforcements together by fusion or adhesion, C) having the thickness of a board material reduced after a filling process and D) forming a low fluidity layer via a filler mixed in a board material. Such properties as allowing the resin flowing in hot press processing to be controlled are provided to a material for manufacturing printed wiring boards of the present invention or to a volatile ingredient contained therein to allow the thickness of a board material to be reduced efficiently after a filling process.