PURPOSE: To provide stable waterproofness even when an execution worker lacks a skill or has carelessness or even when presser concrete is applied.

CONSTITUTION: Terminal sections of asphalt waterproof sheets 3, 4 are lap- connected together by heat fusion, then the outer surface of the end section of the upper asphalt waterproof sheet 4 of the connection section and the surface of the portion continued to the connection section of the lower asphalt waterproof sheet 3 are heated, and the surface zone of the asphalt layer is melted. The liquid of an ordinary temperature hardening material is poured while the surface zone of the asphalt layer is melted, a film 5 of the ordinary temperature hardening material is formed astride both outer surfaces, and the film 5 is fused to the asphalt layer.