In this work we report on an ultrashort pulsed laser annealing-driven devitrification of thin film $Cu_{67}Zr_{33}$ metallic glass characterized by micro-beam X-ray diffraction and electron microscopy techniques. The essential feature of ultrashort pulsed laser annealing is ultrafast heating ($10^{14} K/s$) by femtosecond optical excitation followed by extremely rapid cooling ($10^{10–12} K/s$) due to heat dissipation into the film substrate. During repetitive optical excitation, we take X-ray diffraction snapshots of the intermediate, frozen-in stages of the glass-crystal transformation to study its kinetics. A quantitative analysis of the diffraction patterns supported by electron microscopy result shows that the glass-crystal transformation proceeds by a rapid formation of an energetically favourable layer of crystalline $Zr_{O2}$ on the free surface of the glassy film accompanied by nucleation and growth of fcc-Cu in the residual amorphous matrix. We demonstrate that at low effective annealing temperatures the devitrification kinetics of both products is correlated, while at high temperatures they decouple and $Zr_{O2}$ forms an order of magnitude faster than Cu.