The present invention is to provide a microstructure capable of improving the withstand voltage of an insulating substrate while securing fine conductive paths, a multilayer wiring board, a semiconductor package, and a microstructure manufacturing method. The microstructure of the present invention has an insulating substrate having a plurality of through holes, and conductive paths consisting of a conductive material containing metal filling the plurality of through holes, in which an average opening diameter of the plurality of through holes is 5 nm to 500 nm, an average value of the shortest distances connecting the through holes adjacent to each other is 10 nm to 300 nm, and a moisture content is 0.005% or less with respect to the total mass of the microstructure.