In this study, the basic characteristics of Al–10%Si–0.4%Mg alloy fabricated by Selective Laser Melting (SLM) were investigated. First, laser irradiation conditions were optimized for densification by using an SLM machine equipped with a 400 W Yb fiber laser. As a result, SLM specimens with almost 100 % relative density were obtained. Secondly, the microstructures and mechanical properties of the dense specimens were investigated. The ultimate strength (UTS > 450 MPa) and breaking elongation (EL > 10 %) of the as-fabricated SLM specimens were much higher than those of high pressure die casting materials. This is because they had almost 100 % relative density and showed sub-micron order dendrite-cell microstructures. Moreover, the effects of T5/T6 heat treatment on microstructures and mechanical properties were also investigated. The behaviors of heat treatments in the SLM specimens were different from those of cast melting alloys. The EL of the SLM specimens in the T6 condition increased to about 20 % although the UTS decreased.