In this work, a spinel lithium manganese oxide (LMO) used as a lithium adsorbent was prepared with a conventional solid state reaction using lithium carbonate and manganese carbonate as the reactants. A cylinder-type LMO was prepared using water glass (sodium silicate solution) as a binder together with the reactants and examined for its lithium adsorption capacity. The effect of the preparation condition on the adsorption capacity of the LMO powder was investigated. The optimum heating condition for the LMO powder, determined to be 500°C for 4 h, was applied to prepare the cylinder-type LMO. The cylinder-type LMO showed a maximum adsorption capacity of 15.06 mg/g when immersed in lithium-enriched seawater, whereas LMO powder showed a maximum adsorption capacity of 27.62 mg/g under identical conditions. The cylinder-type LMO generally maintained its structure after the acid treatment and the Li adsorption process. Thus, the cylinder-type LMO developed in this study can overcome the limits associated with powder-type adsorbents and may be appropriate for multiple adsorption runs in seawater.