A vital-sign estimation apparatus is provided. The vital-sign estimation apparatus includes a physiological sensing device, a model generation circuit, and a vital-sign estimator. The physiological sensing device is configured to sense at least one physiological feature of an object to acquire at least one bio-signal. The model generation circuit provides a first reference model serving as an estimation mode. The vital-sign estimator generates vital-sign data according to the at least one bio-signal by using the estimation model. In response to the vital-sign estimation apparatus receiving calibration data, the model generation circuit changes the estimation model according to the calibration data thereby calibrating the vital-sign estimator.
