A lead frame includes a plate portion provided with a first surface and a second surface, the second surface being opposite to the first surface; a protruding portion integrally formed with the plate portion to be protruded from the first surface of the plate portion, wherein a surface of the lead frame includes a work affected layer existing region at which a work affected layer is formed, and a work affected layer non-existing region at which a work affected layer is not formed, wherein a front end surface of the protruding portion is the work affected layer existing region, wherein a region of the first surface at which the protruding portion is not formed is the work affected layer non-existing region, and wherein the second surface of the plate portion includes the work affected layer non-existing region.