A cushioning device to be located between a vibration target member, which is a vibration source, and a connection target member, which is a connection target, the cushioning device connecting the vibration target member and the connection target member to each other and cushioning transmission of a vibration from the vibration target member to the connection target member, the cushioning device comprising a cushioning member cushioning the vibration, a joining member joining the cushioning member and the connection target member to each other, and a collar member located between a tightening member tightened to the vibration target member and the cushioning member; wherein: the joining member includes: a first holding portion holding the connection target member on a diametrically outer side; a second holding portion holding the cushioning member on a diametrically inner side; and a coupling portion coupling the first holding portion and the second holding portion to each other; the collar member includes a tightening member insertion portion, provided on the diametrically inner side, allowing the tightening member to pass therethrough, and the cushioning member, provided on the diametrically outer side holding portion, holding a collar member attaching portion; the cushioning member is formed of a wiring member having a spiral shape as seen in a plan view, and includes the collar member attaching portion, provided at a diametrically central part of the spiral shape as seen in a plan view, allowing the collar member to be attached thereto and a held portion held by the second holding portion, the held portion being provided in a diametrically outer part of the spiral shape as seen in a plan view; and at least a part of the spiral shape as seen in a plan view of the cushioning member has a high spring portion having a spring constant higher than that of another portion of the spiral shape as seen in a plan view. the joining member includes: a first holding portion holding the connection target member on a diametrically outer side; a second holding portion holding the cushioning member on a diametrically inner side; and a coupling portion coupling the first holding portion and the second holding portion to each other; a first holding portion holding the connection target member on a diametrically outer side; a second holding portion holding the cushioning member on a diametrically inner side; and a coupling portion coupling the first holding portion and the second holding portion to each other; the collar member includes a tightening member insertion portion, provided on the diametrically inner side, allowing the tightening member to pass therethrough, and the cushioning member, provided on the diametrically outer side holding portion, holding a collar member attaching portion; the cushioning member is formed of a wiring member having a spiral shape as seen in a plan view, and includes the collar member attaching portion, provided at a diametrically central part of the spiral shape as seen in a plan view, allowing the collar member to be attached thereto and a held portion held by the second holding portion, the held portion being provided in a diametrically outer part of the spiral shape as seen in a plan view; and at least a part of the spiral shape as seen in a plan view of the cushioning member has a high spring portion having a spring constant higher than that of another portion of the spiral shape as seen in a plan view.