Method of producing a waterproof sheet for a tunnel which is to be built by a cut and cover tunneling method comprising a base sheet containing a synthetic resin which is an ethylene-vinyl acetate copolymer having a content of a structural unit derived from vinyl acetate of 30% by mass or more, and having on a surface thereof a silica-containing surface layer containing silica having a silicon dioxide content of 90% by mass or more, the method comprising a step of coating the base sheet with a silica dispersion liquid and drying under heating to form the silica-containing surface layer, the silica dispersion liquid comprising (i) to (iii): (i) silica having a silicon dioxide content of 90% by mass or more, dispersed in (ii) an organic solvent exhibiting dissolution action on said ethylene-vinyl acetate copolymer of the base sheet, and (iii) a thickener having affinity with the synthetic resin of the base sheet, the thickener being an ethylene-vinyl acetate copolymer having a content of structural unit derived from vinyl acetate of 30 to 90% by mass, the silica in the silica-containing surface layer being present in a content of from 30 to 200 mg/cm 3, the silica-containing surface layer being formed over a depth of from 5 to 30 μm from the surface of the waterproof sheet, the waterproof sheet having a tensile breaking strength of 20 MPa or more, a tensile breaking elongation of from 10 to 50%, a tear strength of 50 N or more and a watertightness on deterioration in evenness or levelness of 10 mL/day or less, and a mortar adhesion strength of 15 N/cm or more, wherein the tensile breaking strength, the tensile breaking elongation and the tear strength are measured according to JIS L1096 with a measurement machine, Model 5566, produced by Instron Japan, Co., Ltd., in an environment at a temperature of 20 °C and a humidity of 65 %, the tensile breaking strength is obtained by dividing the actual tensile strength at break by the cross sectional area of the sample, and the watertightness is measured in accordance with point 9 of the description describing the "Method for measuring Watertightness on Deterioration in Evenness or Levelness for Waterproof Sheet ", wherein the mortar adhesion strength of the waterproof sheet is an average peeling strength per 1 cm of the waterproof sheet upon peeling the waterproof sheet from one end at an angle of 180° and a speed of 10 mm/min by 2 cm off from a cured product of a mortar liquid, which is prepared by mixing 100 parts by mass of Portland cement, 200 parts by mass of standard sand and 50 parts by mass of water, and is then cast to a thickness (depth) of 4 cm on the silica-containing surface layer as the concrete adhesion surface of the waterproof sheet cut into a prescribed dimension, followed by curing in a sealed state at 20 °C for 28 days. (i) silica having a silicon dioxide content of 90% by mass or more, dispersed in (ii) an organic solvent exhibiting dissolution action on said ethylene-vinyl acetate copolymer of the base sheet, and (iii) a thickener having affinity with the synthetic resin of the base sheet, the thickener being an ethylene-vinyl acetate copolymer having a content of structural unit derived from vinyl acetate of 30 to 90% by mass,