We report direct observations of laser-induced coherent lattice vibration in gold nanocrystals on the fused quartz substrate using picoseconds time-resolved X-ray diffraction. The single-layered gold nanocrystal film is formed by means of vapor-evaporated gold film. The lattice constant change and vibration period of lattice constants of 111, 200, 311, 220, and 222 of gold nanocrystals after femtosecond laser irradiation at 400 nm are almost similar within nanosecond region. These results indicate that the strain generated from laser-induced expansion within a few picoseconds and propagates into the finite size gold crystals. The feature of these photo-induced lattice vibrations in gold nanocrystals is discussed.