A manufacturing method of a semiconductor package includes etching a first surface and a side surface of a base substrate, the base substrate including the first, a second and the side surfaces positioned between the first and the second surfaces, the base substrate containing a metal, attaching a metal different from the metal contained in the base substrate to the first and the side surfaces, disposing a semiconductor device on the second surface, the semiconductor device having an external terminal, forming a resin insulating layer sealing the semiconductor device, forming a first conductive layer on the resin insulating layer, forming an opening, exposing the external terminal, in the first conductive layer and the resin insulating layer; and forming a metal layer on the first and the side surfaces, on the first conductive layer and in the opening.