A collision avoidance ECU sets a target relative deceleration to a first target value when a brake control starting condition is satisfied, and carries out a first brake control for bringing a relative deceleration closer to the target relative deceleration. When a reference relative deceleration with reference to the relative deceleration at a first point in time has reached a specified relative deceleration, the collision avoidance ECU determines a greater value for a second target value when the amount of change in deceleration, which is the amount of change in the reference relative deceleration at the point in time, is small than when the amount of change in deceleration is large. The collision avoidance ECU then sets the target relative deceleration to the second target value, and carries out a second brake control for bringing the relative deceleration closer to the target relative deceleration.