ABNORMALITY DETERMINATION DEVICE

An abnormality determination device is applied to a vehicle provided with a transmission configured to transmit power by rotation of a shaft. The abnormality determination device includes a processor and a memory. The memory configured to store mapping data that is data that defines mapping learned by machine learning. The processor is configured to execute an acquisition process and a determination process. The acquisition process is a process of acquiring a variable indicating a time-series data of a rotation speed of the shaft and using the variable as a value of an input variable of the mapping. The determination process is a process of determining whether an abnormality has occurred in the transmission based on a value of the output variable acquired using the value of the input variable and the mapping.