LOOKING AWAY DETERMINATION DEVICE, LOOKING AWAY DETERMINATION SYSTEM, LOOKING AWAY DETERMINATION METHOD, AND STORAGE MEDIUM

A looking away determination device includes: a looking away determination unit that determines that a driver is in a looking away state when a proportion of an image in which a face having a degree of certainty equal to or greater than a threshold value is shown with respect to a plurality of images obtained by imaging the driver, the degree of certainty serving as an index of face likeness; and an updating unit that updates the threshold value based on a degree of certainty of a face shown in an image obtained by imaging the driver.