To provide a waterproof sheet fixing method which strongly bond a waterproof sheet to a substrate even if the waterproof sheet is formed of a vulcanized rubber sheet.

The waterproof sheet fixing method is comprised of a connection member fixing step of fixing a connection member to the substrate, a sheet laying step of laying the waterproof sheet 14 to the substrate, and a bonding step of abutting an electromagnetic induction heater S on a connection member fixing portion of the waterproof sheet 14, and heating the heater S to bond the waterproof sheet 14 to the connection member 2. According to the method, the waterproof sheet 14 is formed of the vulcanized rubber sheet. Further, the connection member 2 is formed of a metallic material 4 which can be heated by electromagnetic induction, and has an adhesive resin layer 6 formed on a front surface thereof, which has a radical polymerized functional group.