A refrigerant gas is collected and a compressor is removed from a discarded refrigerator, a heat-insulating housing including a heat insulator is cut/processed and separated into a plurality of pieces, and the pieces are compressed/processed by compression rollers opposing each other so as to collect a gas contained in the heat insulator. In accordance with this method, substantially no gas contained in the heat insulator is diffused at the time of cutting the heat-insulating housing, and the gas can be collected at a high concentration because it is collected by being allowed to leak out at the time of compressing. Furthermore, by using the compression rollers, closed-cells in the heat insulator can be crushed easily, thereby collecting the gas completely and reliably. Thus, it is possible to collect a foaming gas contained in the heat insulator efficiently and disassemble a refrigerator at low cost without increasing the size of-equipment and an installation space.