The present invention provides a device and a method for enhancing the resolution of the digital signal of a digital encoder. The device comprises a digital encoder which outputs a fundamental position signal. Beside, the device comprises a selected integral circuit which receives the fundamental position signal to produce an integral signal according to a predetermined way, a reset circuit which resets the select integral circuit according to the fundamental position signal, a level shift and gain circuit which transforms and amplifies the level of the integral signal to produce a processing signal, and an analog-digital converter which receives the processing signal to produce an expanding position signal. In the device, the resolution of the expanding position signal is higher than the resolution of the fundamental position signal, so that it enhances the resolution of the digital signal of the digital encoder.