The laser-induced damage of epitaxially grown GaN semiconductor material is investigated for the first time by illumination of the c-plane by sub-picosecond laser pulses at the wavelength of 400 nm. The surface damage was investigated by optical and atomic force microscopies. The threshold fluence for ablation damage is determined to be ∼5.4 J/cm² for pulse width of 150 fs. An application is demonstrated for laser-beam processing by the formation of clean dips on the GaN surface to depths of 240 nm in a single shot.