A substrate for mounting an electronic component includes a base material including insulating resin, a first conductor layer formed on first surface of the material, a second conductor layer formed on second surface of the material, and a metal block inserted into a hole penetrating through the first conductor, material and second conductor such that the metal block is fitted in the hole. The material has a bent portion in contact with the metal block in the hole such that the bent portion is bending toward the second conductor, the metal block has surface on first conductor side such that the surface has an outer peripheral portion having a curved-surface shape, and the hole has a first fitting inlet on the first conductor layer side and a second fitting inlet on second conductor side and that the metal block is positioned in contact with the second fitting inlet.