A collision avoidance control device for a vehicle comprising: a determiner configured to determine whether to perform collision avoidance control to avoid collision with an obstacle ahead, based on data acquired in traveling; and a brake controller configured to, upon determination to perform the collision avoidance control by the determiner, control at least a brake device to decelerate the vehicle at a first deceleration (Dpp) for a pre-brake period (ts1-ts2) and to decelerate, after the pre-brake period (ts1-ts2), the vehicle at a second deceleration (Dp) greater than the first deceleration (Dpp), and give, to the brake device, an operational instruction to generate a third deceleration (Dpf) smaller than the first deceleration (Dpp) for a prefill period (tp-ts1) that is immediately before the pre-brake period (ts1-ts2), characterized in that when receiving a brake request from a driver at the prefill period (tp-ts1) during which the vehicle is decelerated with the third deceleration (Dpf), the brake controller controls at least the brake device to decelerate, until a start of the pre-brake period (ts1-ts2), the vehicle at a deceleration calculated by adding the third deceleration (Dpf) and a fourth deceleration (Db) corresponding to the brake request, and decelerate the vehicle at the first deceleration (Dpp) after the start of the pre-brake period (ts1-ts2). a determiner configured to determine whether to perform collision avoidance control to avoid collision with an obstacle ahead, based on data acquired in traveling; and a brake controller configured to, upon determination to perform the collision avoidance control by the determiner, control at least a brake device to decelerate the vehicle at a first deceleration (Dpp) for a pre-brake period (ts1-ts2) and to decelerate, after the pre-brake period (ts1-ts2), the vehicle at a second deceleration (Dp) greater than the first deceleration (Dpp), and give, to the brake device, an operational instruction to generate a third deceleration (Dpf) smaller than the first deceleration (Dpp) for a prefill period (tp-ts1) that is immediately before the pre-brake period (ts1-ts2), control at least a brake device to decelerate the vehicle at a first deceleration (Dpp) for a pre-brake period (ts1-ts2) and to decelerate, after the pre-brake period (ts1-ts2), the vehicle at a second deceleration (Dp) greater than the first deceleration (Dpp), and give, to the brake device, an operational instruction to generate a third deceleration (Dpf) smaller than the first deceleration (Dpp) for a prefill period (tp-ts1) that is immediately before the pre-brake period (ts1-ts2), characterized in that when receiving a brake request from a driver at the prefill period (tp-ts1) during which the vehicle is decelerated with the third deceleration (Dpf), the brake controller controls at least the brake device to decelerate, until a start of the pre-brake period (ts1-ts2), the vehicle at a deceleration calculated by adding the third deceleration (Dpf) and a fourth deceleration (Db) corresponding to the brake request, and decelerate the vehicle at the first deceleration (Dpp) after the start of the pre-brake period (ts1-ts2). decelerate, until a start of the pre-brake period (ts1-ts2), the vehicle at a deceleration calculated by adding the third deceleration (Dpf) and a fourth deceleration (Db) corresponding to the brake request, and decelerate the vehicle at the first deceleration (Dpp) after the start of the pre-brake period (ts1-ts2).