DRIVING ASSISTANCE DEVICE AND DRIVING ASSISTANCE METHOD

A driving support device which more appropriately manages the necessity of a driving support related to collision avoidance and which effectively restrains unnecessary activation of the driving support is disclosed. The driving support device performs a collision avoidance support on a vehicle (10) relative to a leading vehicle (60) present in a travelling direction of the vehicle (10), based on a time-to-collision Ta as a time that the vehicle (10) takes to collide with the leading vehicle (60). A lateral change amount calculation portion (23) detects a relative lateral velocity Vy, which is a relative time-dependent change amount between the vehicle (10) and the leading vehicle (60). A storage portion (40) stores therein a steering time T1, which is a time required for the vehicle (10) to avoid the leading vehicle (60) by steering. The storage portion (40) stores therein an activation threshold TH1, which is a threshold to determine activation of the driving support based on the relative lateral velocity Vy. When a relative lateral velocity Vy at a time when the time-to-collision Ta is the steering time T1 or more is the activation threshold TH1 or more, a support management portion (50) restrains the activation of the driving support.