A driving support device that performs a driving support on a vehicle to avoid collision with an object present in a travelling direction of the vehicle based on a time-to-collision as a time until the vehicle and the object collide with each other, the driving support device characterized by comprising: a lateral change detection portion configured to detect a lateral relative time-dependent change amount between the vehicle and the object in a lateral direction perpendicular to the travelling direction of the vehicle; a first storage portion in which a steering time is stored as a time required for the vehicle to avoid the object by steering; a second storage portion in which an activation threshold is stored as a threshold used to determine whether activation of the driving support is performed based on the lateral relative time-dependent change amount detected by the lateral change detection portion; and a support management portion configured to restrain the activation of the driving support at a time when the lateral relative time-dependent change amount detected, when the time-to-collision is the steering time or more, is the activation threshold or more, wherein: a target region is defined ahead of the vehicle in the traveling direction, the target region being sectioned by a front part of the vehicle and movement loci of right and left front edges of the vehicle, the movement loci being in accompany with steering of the vehicle over the steering time; and the support management portion is configured to replace the steering time to be compared with the time-to-collision with a time obtained according to a position at which the object enters the target region with respect to the vehicle width center, wherein the time to be replaced is the steering time in a case where the entering position is a vehicle width center of the vehicle, and when the entering position is away from the vehicle width center, the time to be replaced becomes shorter than the steering time. a lateral change detection portion configured to detect a lateral relative time-dependent change amount between the vehicle and the object in a lateral direction perpendicular to the travelling direction of the vehicle; a first storage portion in which a steering time is stored as a time required for the vehicle to avoid the object by steering; a second storage portion in which an activation threshold is stored as a threshold used to determine whether activation of the driving support is performed based on the lateral relative time-dependent change amount detected by the lateral change detection portion; and a support management portion configured to restrain the activation of the driving support at a time when the lateral relative time-dependent change amount detected, when the time-to-collision is the steering time or more, is the activation threshold or more, wherein: a target region is defined ahead of the vehicle in the traveling direction, the target region being sectioned by a front part of the vehicle and movement loci of right and left front edges of the vehicle, the movement loci being in accompany with steering of the vehicle over the steering time; and the support management portion is configured to replace the steering time to be compared with the time-to-collision with a time obtained according to a position at which the object enters the target region with respect to the vehicle width center, wherein the time to be replaced is the steering time in a case where the entering position is a vehicle width center of the vehicle, and when the entering position is away from the vehicle width center, the time to be replaced becomes shorter than the steering time. a target region is defined ahead of the vehicle in the traveling direction, the target region being sectioned by a front part of the vehicle and movement loci of right and left front edges of the vehicle, the movement loci being in accompany with steering of the vehicle over the steering time; and the support management portion is configured to replace the steering time to be compared with the time-to-collision with a time obtained according to a position at which the object enters the target region with respect to the vehicle width center, wherein the time to be replaced is the steering time in a case where the entering position is a vehicle width center of the vehicle, and when the entering position is away from the vehicle width center, the time to be replaced becomes shorter than the steering time.