Selective laser melting (SLM) is a manufacturing technique which suitable for fabricating complex machinery parts. Take advantage of this feature it is being actively investigated to weight reduction of parts by combining with structural optimization. Accordingly application to SLM of 7075 Al alloy as a light material having high mechanical strength is expected. However it was reported that micro cracks had occurred in molded parts when processed 7075 Al alloy with SLM. To solve this problem we focused on Si addition. Since Al alloy currently often used in the SLM were containing Si at close to eutectic composition such as AlSi10Mg and AlSi12; therefore 7075+5Si alloy (added 5.0 wt% of Si to 7075 Al alloy) seems to have effect of suppressing cracks. In result of this study processing high density and crack-free 7075+5Si alloy objects by SLM was achieved.