According to one embodiment, in a constricted part of a globe, one end is set to a minimum diameter, the other end is set to a maximum diameter, and a diameter thereof increases from the one end side to the other end side. The constricted part of the globe is concaved into the inside of an imaginary straight line connecting an outer edge of the one end and an outer edge of the other end when viewed in section. A light source part includes a semiconductor light-emitting element and is contained in the globe so that a light-emitting part is positioned between both the ends of the constricted part of the globe. A cap is positioned on one end side of the globe.