An optical storage medium having a three-dimensional data pattern, and fabrication method thereof. The optical storage medium includes a substrate and a plurality of recording layers, each constituting a fluorescent oligomer. Due to the high quantum yield and high stock shift of the fluorescent oligomer, the recording layers emit intensive fluorescent signals when the optical storage medium is illuminated with reading beams. Accordingly, the recording sensitivity and the readout characteristics of optical storage mediums are improved without additional signal-amplifying structures or materials.