A reducing-agent injector gasket to be interposed between a reducing-agent injector capable of injecting a reducing agent and an injector retention section provided in an exhaust pipe, the injector retention section including a retaining wall having an injector opening that allows the reducing agent to be injected from the reducing-agent injector into the exhaust pipe and a retention bolt projecting beyond the retaining wall to retain the reducing-agent injector, the reducing-agent injector gasket comprising: a first plate to make contact with the retaining wall, the first plate having a first opening that allows the reducing agent to be injected, in cooperation with the injector opening of the retaining wall, and a first bolt insert-through hole that allows the retention bolt to be inserted through the first bolt insert-through hole; a second plate disposed in a position closer to the reducing-agent injector than the first plate, the second plate having a second opening that allows the reducing agent to be injected, in cooperation with the injector opening, and a second bolt insert-through hole that allows the retention bolt to be inserted through the second bolt insert-through hole; and a spacing keeping member that keeps a spacing between the first plate and the second plate so as to form a heat insulation space between the first plate and the second plate, the heat insulation space having a shape that enables at least a part of the heat insulation space to communicate with the outside of the reducing-agent injector gasket between the first plate and the second plate in a state in which the reducing-agent injector is retained by the injector retention section via the reducing-agent injector gasket, characterized in that the spacing keeping member has a lower heat conductivity compared to the heat conductivity of the first plate and second plate. a first plate to make contact with the retaining wall, the first plate having a first opening that allows the reducing agent to be injected, in cooperation with the injector opening of the retaining wall, and a first bolt insert-through hole that allows the retention bolt to be inserted through the first bolt insert-through hole; a second plate disposed in a position closer to the reducing-agent injector than the first plate, the second plate having a second opening that allows the reducing agent to be injected, in cooperation with the injector opening, and a second bolt insert-through hole that allows the retention bolt to be inserted through the second bolt insert-through hole; and a spacing keeping member that keeps a spacing between the first plate and the second plate so as to form a heat insulation space between the first plate and the second plate, the heat insulation space having a shape that enables at least a part of the heat insulation space to communicate with the outside of the reducing-agent injector gasket between the first plate and the second plate in a state in which the reducing-agent injector is retained by the injector retention section via the reducing-agent injector gasket, characterized in that the spacing keeping member has a lower heat conductivity compared to the heat conductivity of the first plate and second plate.