An unusual-noise determination device for a vehicle that performs unusual-noise determination to determine whether a power transmission system of the vehicle is generating unusual noise. The unusual-noise determination device includes an execution device and a memory device. The memory device stores a neural network that uses the maximum sound pressure and the excess ratio as inputs, and outputs a determination result variable, which is a variable indicating a result of the unusual-noise determination. The neural network is a trained neural network that has been trained using various values related to each of multiple vehicles as training data. The execution device is configured to perform the unusual-noise determination based on an output of the trained neural network that uses, as inputs, the maximum sound pressure and the excess ratio.