Driver assistance device and driver assistance method for vehicle

The driver assist ECU determines whether there is another vehicle on the collision course based on the other vehicle information. ECU determines whether a predetermined execution condition for executing the collision avoidance assist operation is satisfied when it is determined that there are other vehicles on the collision course, and starts executing the collision avoidance assist operation when it is determined that the execution condition is satisfied. ECU changes the execution condition based on an approaching direction determination result as to whether the other vehicle on the collision course is approaching from the direction of the driver's seat of the host vehicle or is approaching from the direction on the passenger seat of the host vehicle, and a visual perception determination result as to whether the probability that the driver of the host vehicle has visually perceived the other vehicle on the collision course is high.