A diagnostic image generating apparatus, a medical image system, and a beamforming method are provided. The diagnostic image generating apparatus includes a transmitting unit configured to transmit a modulated transmission signal to a subject, a reception beamforming unit configured to form a reception beam by beamforming echo signals reflected from the subject, a point spread function (PSF) estimating unit configured to estimate a PSF for each region according to the formed reception beam, a filtering unit configured to filter the formed reception beam according to the estimated PSF, and a diagnostic image generating unit configured to generate a diagnostic image according to the filtered reception beam.
