In this study, the selective electron beam melting (SEBM) process was used to fabricate Inconel 718 superalloy, and their microstructures and creep resistances were investigated. The proper SEBM condition ensuring a relative density higher than 99.9% was found in electron beam current range of 24–30 mA at a scanning speed of 4500 mm/s and a preheat temperature of 1025 °C, from which the SEBMed Inconel 718 exhibited an unidirectional columnar grain microstructure with a strong <100> texture along building direction. It was suggested that the local thermal condition during solidification after SEBM facilitates a continuation of epitaxial growth of crystals on layer beneath. The γ″ precipitates formed in the as-built condition regardless of focus offset, and their size increased with increasing focus offset from 1 to 12 mA. The creep rupture life of the as-built sample fabricated with focus offset of 12 mA showed 2 times longer than that of conventional forged Inconel 718 subjected to full heat treatment under creep condition of 650 °C/700 MPa. EBSD analysis on the crept samples indicated that strain accumulation was significant at the porosities and the high-angle grain boundaries. Additionally, the grain boundaries inclined to loading axis were more damaged during creep. The γ″ particles were occasionally sheared by matrix dislocations with Burger vector of a/2<110>, without leaving stacking faults behind. The enhanced creep resistance of SEBMed Inconel 718 superalloy can be attributed to the columnar microstructure with a strong <100> texture and the high density of dislocations resulted from strong interaction with the γ″ particles.