Inattention determining apparatus

An inattention determination device (10) includes a sight direction detecting unit (23) that detects a sight direction of a driver, and an inattention determining unit (24) that measures an inattention continuation time from a time point when the sight direction is a predetermined inattention direction to a time point when the sight direction deviates from the predetermined inattention direction and becomes a direction other than the inattention direction and determines that the driver is inattentive when the intention continuation time is equal to or more than a predetermined time (TB). The inattention determining unit (24) maintains measurement of the inattention continuation time when the sight direction is changed at a speed higher than a predetermined movement speed from the predetermined inattention direction to a direction other than the inattention direction or when the sight direction is momentarily a direction other than the inattention direction.