A driver monitoring device includes a processor configured to calculate a degree of complexity of a situation around a vehicle based on at least one image generated by a camera mounted on the vehicle and representing the situation, set an alert condition for urging a driver of the vehicle to pay attention so that the alert condition is relaxed as the degree of complexity increases, detect a behavior of the driver, and notify the driver of an alert for paying attention via a notification device when the behavior of the driver satisfies the alert condition.
