alpha-Tricalcium phosphate (alpha-TCP) macroporous ceramic scaffold was chemically treated with a buffered solution at pH = 4. Mesopores were formed in the scaffold after the treatment to result in a remarkable increase in surface area of the scaffold. The increase in the surface area is caused by precipitation of octacalcium phosphate (OCP). Bimodal pore size distribution consisting of mesopores and macropores obtained by the treatment of alpha-TCP scaffold having higher initial porosity brought about high adsorption of bovine serum albumin (BSA) than monomodal pore size distribution of mesopores. Adsorption of BSA, acidic protein, was suggested to result from crystallographic characters of OCP.