CrMnFeCoNi high entropy alloy (HEA) which had nano oxide particles formed during additive manufacturing process was fabricated using a selective laser melting (SLM) process (hereinafter SLM Cantor HEA). The microstructure of the fabricated SLM Cantor HEA and the wear properties according to the applied load (5 N, 15 N) were investigated. SLM Cantor HEA was consist of nano-size oxides and high dislocation density, resulting in superior hardness compared to conventional processed CrMnFeCoNi HEA. As a result of the wear test, it showed abrasive and oxidative wear behavior regardless of applied load. But in case of 15 N load condition, it showed more finer worn microstructure with increased wear load, and had a contradictory effect on each friction coefficient and wear rate. Based on the above results, the wear mechanism of in-situ oxide reinforced SLM Cantor HEA was discussed in relation with the microstructure.