A light-emitting-element mounting package includes a substrate and a frame that are each made of a metal. The substrate includes a front surface and a back surface that oppose each other, and is provided with a mounting portion for a light emitting element at the front surface. The frame stands on the front surface of the substrate and includes an inner side surface that surrounds the mounting portion and an outer side surface. A substrate-side end portion of the frame includes a curved inclined surface (inclined portion) in a region near the outer side surface. The curved inclined surface is inclined toward a center of the frame in a thickness direction. A silver solder (joining material) is provided between the front surface of the substrate and the frame.