An adsorbent for an oral administration, comprising a surface-modified spherical activated carbon wherein an average diameter is 0.01 to 1 mm, a specific surface area determined by a BET method is 700 m2/g or more, a volume of pores having a pore diameter of 7.5 to 15000 nm is from 0.25 mL/g to 1.0 mL/g, a total amount of acidic groups is 0.30 to 1.20 meq/g, and a total amount of basic groups is 0.20 to 0.7 meq/g, is disclosed.