Abstract: An electronic component package includes a case having a cavity portion including an electronic component therein, and a lid member which is fusion-welded to the case via a fusion-welding layer to hermetically seal the cavity portion. The case has a first metal layer laminated on the case so as to be exposed on the open side at the cavity portion. The lid member has a core portion, and a second metal layer laminated on a side of the core portion facing the case. The fusion-welding layer has a soldering material layer formed of a soldering material, and first and second intermetallic compound layers disposed on opposite sides of the soldering material layer as a result of diffusion of a major component of the soldering material into the first metal layer and the second metal layer.