To provide a connecting device of a shaft to a hub which can make disconnection of the shaft from the hub with no addition of a tool for pulling apart.

This invention relates to a connecting device of a shaft to a hub seating the shaft provided with an outer surface part in a first hole part 6 of the hub 3. A tightening screw 19 is provided for tightening, its head part, in a tightened condition seating a screwed shaft 22 in a screwed hole 18 of the shaft 14, is supported onto a support disc 11 held immovably axially on the hub 3. A nut 23 is seated on the screwed shaft 22 between the support disc 11 and the shaft 14. This nut 23 is immovably held. When the tightening screw 19 is operated in the disconnection direction, the nut 23 abuts to the support disc 11, as a result the hub 3 and the shaft 14 are moved to separate from each other.