Abstract: The object is to provide a brace which allows its installment to an object portion and its detachment therefrom to be carried out easily. In a brace including a brace body 3 which is attachable between attaching object portions of a structure, at each one of opposed end portions of the brace body 3, there is provided a contact attaching portion to be attached to the attaching object portion. The brace body 3 includes an expandable urging mechanism S which can be expanded to urgedly extend the brace body 3 along a longitudinal direction thereof, with the two contact attaching portions attached to the attaching object portions and a prestress introducing mechanism P which can be switched over between a state for introducing a compressive prestress to the brace body 3 along the longitudinal direction thereof and a state for releasing the introduced prestress. At least a state switchover control portion 22 of the prestress introducing mechanism is provided to be exposed outside the brace body 3.