A light-emitting device of high light extraction efficiency comprises a first substrate, a light-emitting chip positioned on the first substrate and configured to emit light beams, a fluorescent material positioned on the light-emitting chip, a photonic crystal positioned on the fluorescent material and a reflector positioned on the photonic crystal and configured to reflect the light beam to the fluorescent material. The first substrate is preferably a metallic cup, and the light-emitting chip is positioned at the bottom of the metallic cup. The photonic crystal includes a second substrate and a plurality of protrusions positioned on the second substrate. Each of the protrusions includes a bottom end positioned on the second substrate and a tip portion smaller than the bottom end. The plurality of protrusions can be triangular pillars, semicircular pillars, sinusoid pillars, pyramids, or cones.