A generator set includes a permanent soundproof housing for housing a portable engine generator therein. The portable engine generator has wheels for moving the same and can be operated in the permanent soundproof housing. The portable engine generator can be taken out of the permanent soundproof housing by pulling the portable engine generator out of the permanent soundproof housing in a direction transverse to a direction of advance of the wheels, and thereafter moving the portable engine generator in the direction of advance of the wheels.