Catalyst temperature estimation apparatus

A catalyst temperature estimation apparatus estimating a catalyst temperature of an exhaust gas purification device, the exhaust gas purification device being disposed in an exhaust passage of an internal combustion engine, the internal combustion engine including an injector injecting a fuel and having a function of a fuel cut configured to shut off a fuel injection from the injector while a vehicle is traveling,

• the catalyst temperature estimation apparatus comprising
• an electronic control unit including a microprocessor and a memory connected to the microprocessor, wherein
• the microprocessor is configured to perform
• acquiring a parameter representing an operation state of the internal combustion engine, and
• obtaining an estimated value of the catalyst temperature based on the parameter,
• the obtaining including maintaining the estimated value at a start of the fuel cut until the operation state after the fuel cut becomes a predetermined operation state when the fuel cut is executed.