To provide the installation structure of a weather-strip excellent in an installation stability and a seal property without cost up especially.

In the installation structure of a weather-strip 12 having a hollow seal part 12b for sealing the boundary part M between a side door panel 11A and a body panel 14 at the closing time of a vehicular side door, the side door panel 11A is installed in the side door in a state extending the door glass G1 of the side door, while covering from a car room outside, upto near the boundary part M and the base 12a of the weather-strip 12 molded integrally with the hollow seal part 12b is held and fixed between the periphery part of the door glass G1 and the side door panel 11A and a glass run 16 for guiding an elevating glass G2 is installed on the lower periphery edge of the door glass G1.