To develop monodisperse amphiphilic polymer particles on which a large amount of lipase could be immobilized, we performed seed polymerizations of glycidyl methacrylate and allyl methacrylate in the presence of nonpolar inert and polar inert solvents. The amphiphilic porous polymer particles, which had both hydrophilic guanidino groups and hydrophobic stearoyl groups, were synthesized in the presence of n-decane and had a large amount of macropores with diameters of 50-1000 nm. The amount of lipase immobilized on the amphiphilic particles synthesized in the presence of n-decane was 3.85 times that of the lipase immobilized on the amphiphilic particles synthesized in the absence of a solvent. The immobilized lipase prepared with the amphiphilic particles synthesized in the presence of n-decane exhibited a high transesterification activity in n-hexane and could be used repeatedly without a considerable activity loss.