To enable to use a lip type seal at installation positions where shaft diameters are same but shaft hole diameters are different, an installation structure is made such that a lip type seal (1) is installed to an inner periphery of a shaft hole (72) via a cartridge (51) arranged at an outer peripheral side of the lip type seal, the cartridge (51) has a large-diameter tube portion (54) and a small-diameter tube portion (52) via a step portion (53), and is fitted to the inner periphery of the shaft hole (72) by an outer peripheral surface of the large-diameter tube portion (54), while the lip type seal (1) is fitted to an inner peripheral surface of the small-diameter tube portion (52), and only a diameter of the large-diameter tube portion (54) is set in conformity to a diameter of a shaft hole to be installed.