A light bulb includes an enclosure, a heat-dissipating unit, and a lamp unit. The enclosure extends along an axis, and defines an inner space therein. The heat-dissipating unit includes a hollow first heat-dissipating element disposed in the inner space, a second heat-dissipating element surrounded by the first heat-dissipating element and extending along the axial direction, and an end heat-dissipating element mounted to the second heat-dissipating element at a distal end thereof. The lamp unit includes a first circuit board disposed at a periphery of the first heat-dissipating element, a second circuit board mounted on the end heat-dissipating element, and a plurality of light-emitting elements mounted on the first and second circuit boards for emitting light beams.