PURPOSE: To provide a waterproof structure for grommet which surely prevents the penetration of moisture when a wire harness is curved, and has excellent working property.

CONSTITUTION: A grommet 11 has a radially extended hole 11d provided on a panel installing part 11b to be mounted on a through hole 7a provided on a wall part 7; and a radially contracted hole 11e provided on a wire harness insert part 11c protruded from the panel installing part, and a wire harness 2 is inserted through the radially extended hole and the radially contracted hole. A first filler layer 15 consisting of a liquefied hardening filler having a short hardening time is provided on the radially contracted hole side of the radially extended hole. A second filler layer 16 consisting of a liquefied hardening filler having high permeability is laminated on the first filler layer. A third filler layer consisting of a liquefied hardening filler having a short hardening time is laminated on the second filler layer.