We present a study of the origin of infrared (IR) emission in the optically normal, infrared luminous galaxy NGC 4418. By decomposing the stellar absorption features and continua in the range of 3600-8000A from the Sloan Digital Sky Survey into a set of simple stellar populations, we derive the stellar properties for the nuclear region of NGC 4418. We compare the observed infrared luminosity with the one derived from the starburst model, and find that star-forming activity contributes only 7% to the total IR emission, that as the IR emission region is spatially very compact, the most possible source for the greater part of the IR emission is a deeply embedded AGN, though an AGN component is found to be unnecessary for fitting the optical spectrum.
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