A nanoscale digital data storage device is provided. In the nanoscale digital data storage device, a storage medium has a polymer layer deposited on a substrate, for writing and reading digital data on and from. A cantilever chip has a plurality of cantilevers arranged therein. Each cantilever is fixed to another substrate at one end and has a tip formed at its free end, for emitting heat according to an applied current. The tips in the cantilever chip are in contact with the storage medium at predetermined bit positions during data writing, and the cantilever chip applies a relatively low current to a tip when the tip writes bit 1 and a relatively high current to the tip when the tip writes bit 0.