Provided is a state determination device for an internal combustion engine. The state determination device includes a storage device, and an execution device. The storage device stores mapping data that is data defining a mapping that outputs a determination result of a state of the internal combustion engine, by using an internal combustion engine state variable as an input. The execution device executes an acquisition process of acquiring the internal combustion engine state variable each time a crankshaft rotates by a specified angle, and a determination process of determining the state of the internal combustion engine based on an output of the mapping using the internal combustion engine state variable as an input. The execution device omits a part of the determination process performed each time the crankshaft rotates by the specified angle when a rotation speed of the crankshaft becomes equal to or higher than a predetermined threshold.