To be provided is a foam waterproofing material superior in waterproofness and flexible enough to be compatible with further minute clearance.The foam waterproofing material according to the present invention is a waterproofing material including a foam having a thickness of 0.1 to 1.0 mm, characterized in that the foam has a micro cell structure with an average cell diameter of 10 to 60 μm and an apparent density of 0.01 to 0.050 g/cm3. In the foam waterproofing material, the repulsive load when compressed to 0.1 mm (0.1 mm-compressive repulsion force) of the foam is preferably 0.01 to 0.1 MPa. The foam preferably has a closed-cell structure or a semi-open and semi-closed-cell structure. In addition, the foam may have a pressure-sensitive adhesive layer on one or both faces thereof. The pressure-sensitive adhesive layer is preferably formed on the foam via a film layer.