A light emitting device mounting board block includes: a lead frame having a plate-shape, the lead frame having a first surface, and a second surface located opposite to the first surface; and a resin molded body located on the first surface of the lead frame, the resin molded body having a recessed portion therein. The resin molded body includes a first lateral wall, a second lateral wall, a third lateral wall and a fourth lateral wall, the first and second lateral walls extending in a length direction, the third and fourth lateral walls extending in a width direction.