To solve the problems of a conventional disc for use in mechanical fixing methods for waterproofing work, wherein its fixing effect can not be fully exhibited because its center could warp inward relative to a building frame when it is screwed or nailed to the building frame; being unable to absorb vibration when acted upon by vibration load; being susceptible to distortion at fixing screws and the building frame; hindering walking on the waterproof sheet because of the uneveness of the sheet.

The waterproof sheet fixing disc is shaped like a Belleville spring so that the disc serves as an elastic body which when screwed establishes a balance between the screwing force and the elastic force of the disc, allowing a person without special tools and skills to install it in the proper position. Using this elasticity, the disc can absorb vibrations that may occur between the building and the waterproof sheet. Moreover, a barrier-free structure can be provided which will not hinder walking on the waterproof sheet.