Spherical beads from poly(γ-methyl-L-glutamatate) alone were prepared using various diluents for macroreticulating by the “suspension and evaporation” method. The porosity and the pore size of the beads obtained were remarkably dependent on the chemical structure of a diluent. This is related to the specific miscibility of a diluent with poly(γ-methyl-L-glutamate). For example, decahydronaphthalene made the beads much more macroporous than tetrahydronaphthalene with similar hydrophobisity: the aromaticity of diluent increases the miscibility. However, it was found that long-chain alkyl compounds with a miscible group such as methyl dodecanoate, oleic acid, linoleic acid, and dialkyl-phthalate were not only very effective for macroreticulating, but also induced narrow pore-size distribution. In addition, the diluent influenced physicochemical properties of the beads to cause specific affinity to proteins.