1. A digital predistortion device for a broadband power amplifier, comprising: a nonlinear power amplifier for amplifying N input signals generated by a random signal generator, and then generating N output signals; an equivalent amplifier model estimator for receiving the N input signals and the N output signals, and estimating characteristics of the nonlinear power amplifier; a coefficient extractor for extracting coefficients of N predistorters using the estimated characteristics of the nonlinear power amplifier; and N predistorters for eliminating or compensating for all or part of the N output signals.