A digital-to-analog converter (DAC) device includes a DAC circuitry, a calibration circuitry, and a randomization circuitry. The DAC circuitry includes a first DAC circuit and a second DAC circuit. The first DAC circuit is configured to generate a first signal according to least significant bits of an input signal. The second DAC circuit is configured to output a second signal. The calibration circuitry is configured to compare the first signal with the second signal, in order to calibrate the second DAC circuit. The randomization circuitry is configured to randomize most significant bits of the input signal, in order to generate first control signals, in which the second DAC circuit is further configured to generate the second signal according to the most significant bits or the first control signals.