The invention aims in establishing a method for modifying biomolecules using a reaction that efficiently modifies biomolecules and is widely applicable. A plurality of cap members 20 is arranged on an outer circumferential surface of a rim 16 in a circumferential direction thereof, diaphragms are disposed inwardly of each cap member 20, and a plurality of sub-air chambers 32 is formed between the rim 16 and the cap members 20 in a rim circumferential direction. The input and output powers are used by a processor to determine an index of power-loss. 1 to 20 kghour, to obtain a plurality of streams of foamed polycarbonate and degassing the streams of foamed polycarbonate in the separating vessel wherein the pressure is 0.