Oxalic acid was used for recovering cobalt from leaching solution of spent lithium ion battery by precipitation method. Crushed powders containing $LiCoO_2$ of spent lithium ion battery were obtained by crushing, magnetic separation and screening process. These powders were dissolved in 2 M $H_2SO_4$ solution with $H_2O_2$ as a reducing agent. After dissolving Co and Li components, the solution of oxalic acid was added. Co(II) in leaching solution could be removed in the form of insoluble oxalates. The precipitate formed was crystalline, compact and easily filtered. With the increase in oxalic acid, the rate of cobalt precipitate increased to 90% at 1:4 mole ratio of Co(II) and oxalic acid concentration. When cobalt ion was precipitated into cobalt oxalate, nickel and copper ions were co-precipitated but there were no co-precipitates of Li, Al and Fe. The amounts of Ni and Cu in the solutions were below 1%. After heat treatment of precipitates at above $250^{circ}C$, cobalt oxalate was changed into cobalt oxide.