A controller executes a fuel introduction process of introducing, in a state in which the crankshaft of an internal combustion engine is rotating, air-fuel mixture that contains fuel injected by a fuel injection valve into the exhaust passage without burning the air-fuel mixture in the cylinder. The controller executes a discharge process of performing spark discharge of an ignition plug at non-combustion ignition timing during the execution of the fuel introduction process. The non-combustion ignition timing is timing within a period in which the air-fuel mixture is not burned in the cylinder even if the spark discharge of the ignition plug is performed.