The invention provides spherical sulfated cellulose which has a high sulfur content and which is excellent for adsorbing proteins, a production process for the same, a protein adsorbing agent containing the above spherical sulfated cellulose and a chromatography apparatus using the same for a filler. More specifically, the invention provides a process for producing spherical sulfated cellulose comprising a step in which spherical cellulose is subjected to at least one sulfate esterification treatment with a mixture of N,N-dimethylformamide and sulfuric anhydride.