The spacer is formed as an elastic member with no ends thereof, which is detachably attached, by exploiting its elastic deformation, onto a printed wiring board to which is fixed an electronic component having a component package, on one of whose surfaces connection terminals are arranged. Since the spacer is attached on the printed wiring board to enclose an electronic component so as to seal a gap formed between the electronic component and a printed wiring board, it is possible to prevent foreign objects entering the gap, so that failures, such as insufficient insulation, caused by such foreign objects are also prevented. Since the spacer is easily removed from the printed wiring board, it is recyclable and economical.