Culture broth of an actinomycete isolate, Nocardia sp. CS682 showed specifically higher antibacterial activity against methicilin resistant Staphylococcus aureus (MRSA). Purified substance from the organism, CS-682, which is active against MRSA and Micrococcus leuteus, is a $C_{28}H_{37}NO_8$ ($M+H^+$, observed: 516.83) and identified as an unusual macrolide antibiotic, nargenicin. The chemical structure of CS-682 was identified by FT-IR, $^1H$-NMR, $^{13}C$-NMR, and ($^1H-^1H$ and $^1H-^{13}H$) COSY. The anti-MRSA activity of CS-682 was stronger than that of oxacillin, vancomycin, monensin, erythromycin, and spiramycin. Phylogenetic analysis showed that strain CS682 is closely related to Nocardia tenerifensis DSM $44704^T$ (98.7% sequence similarity), followed by N. brasiliensis ATCC $19296^T$ (98.4% sequence similarity). The ability of Nocardia sp. CS682 to produce nargenicin was unique.