An inductor built-in substrate includes a core substrate having an opening and a first through hole formed therein, a magnetic resin filling the opening formed in the core substrate such that the magnetic resin has second through holes formed therein, a first through-hole conductor formed in the first through hole of the core substrate and including a metal film formed in the first through hole of the core substrate, and second through-hole conductors formed in the second through holes of the magnetic resin and including metal films formed in the second through holes of the magnetic resin, respectively.