Abstract: A multilayer printed wiring board having an air gap between neighboring printed wiring boards of the multilayer printed wiring board by inserting plated spacers to both end faces of through-hole pads which are provided to each printed wiring board so that each through-hole pad opposes to another through-hole pad on the neighboring printed wiring board. The spacers opposed to each other are joined together by solder, and each spacer has an end surface having a size being smaller than a size of the end surface of each through-hole pad to provide a drop part at the joint part of the spacers, so that melted solder stays at the drop part not flowing toward the board through the side surface of the through-hole pad when the printed wiring boards are integrated to the multilayer printed wiring board under pressure and high temperature.