The present invention relates to a porous manganese oxide-based lithium absorbent and a method for preparing the same. The method includes the steps of preparing a mixture by mixing a reactant for the synthesis of a lithium-manganese oxide precursor powder with an inorganic binder, molding the mixture, preparing a porous lithium-manganese oxide precursor molded body by heat-treating the molded mixture, and acid-treating the porous lithium-manganese oxide precursor molded body such that lithium ions of the porous lithium-manganese oxide precursor are exchanged with hydrogen ions, wherein pores are formed in the lithium-manganese oxide precursor molded body by gas generated in the heat treatment. The porous manganese oxide-based lithium adsorbent according to the present invention is easy to handle and has many more adsorption reaction sites compared to existing molded adsorbents, thus providing high lithium adsorption efficiency.