Fe-based bulk metallic glasses are a very promising material class due to its remarkable soft-magnetic properties. Such material can be obtained by cooling of the melt at very high cooling rate, which can be reached within the framework of one of the most popular additive manufacturing technologies—selective laser melting. To control and manage the key soft-magnetic amorphous-nanocrystalline material parameters determining its magnetic properties—density and amorphization degree, it is vital to understand the influence of production process factors. The impact of the laser spot diameter on the phase composition, density, microstructure, magnetic properties of the FeSiCrB alloy (KUAMET 6B2) was investigated by preparing and studying the samples obtained via selective laser melting. Samples were obtained in nitrogen atmosphere via two selective laser melting systems: one with laser spot diameter of 80 µm and other with laser spot diameter of 40 µm using same basic selective laser melting parameters (excluding hatch distance parameter which was halved in experiment with reduced laser spot diameter). In result, original data on the impact of halving the laser spot diameter on amorphization degree, microstructure, and magnetic characteristics was obtained for different selective laser melting parameters combinations. Complex analysis of the novel obtained results can be used for production development of selective laser melted Fe-based amorphous-nanocrystalline alloys, more precise process parameters optimization and further investigation of the selective laser melted amorphous-nanocrystalline Fe-based alloys.