A cooling device configured to cool, using a coolant, an injection valve that injects an additive includes a rotary member surrounding an outer periphery of the injection valve and extending along the injection valve. The rotary member is supported to be rotatable around the injection valve. A clearance between an outer peripheral surface of the injection valve and an inner peripheral surface of the rotary member defines a passage through which the coolant flows. The rotary member has a rotation imparting part that causes the rotary member to rotate about the injection valve in response to a flow of the coolant.