To provide a method for properly laying a waterproof sheet even under strong wind, achieving enhanced efficiency with reduced working hours, number of processes, and manpower.

A method for laying a waterproof sheet 10, which allows the waterproof sheet 10 to be fixed to a sheet joining member 12 installed to a building frame 1, includes the steps of rolling and spreading the rolled waterproof sheet 10 under pulling tension on an installation place and joining the waterproof sheet 10 to the sheet joining member 12 at each installation place of the sheet joining member 12. In the case of welding by solvent, the waterproof sheet 10 is rolled and spread toward the front of the sheet joining member 12. Immediately after solvent is applied to the sheet joining member 12, the waterproof sheet 10 is rolled on the sheet joining member 12 with the applied solvent so as to pass through. The sheet joining member 12 is then pressed from above the waterproof sheet 10 so that the waterproof sheet 10 is fixed to the sheet joining member 12.