DRIVING ASSISTANCE DEVICE

A driving assistance device includes: an object detecting part that detects an object behind and/or to the left and/or right rear of a host vehicle; an area setting part that sets a warning area behind and/or to the left or right rear of the host vehicle; a notification part that issues a notification when an object is detected within the warning area by the object detecting part; and an area changing part that calculates, based on a variation in curvature of a traveling trajectory of the host vehicle, an area reliable distance defining an area with high reliability, based on the area reliable distance, sets a reference position, and based on a lateral line extending in a turning radius direction of the host vehicle at the reference position, changes a rear end of the warning area.