A driving assisting method using a driving assisting device, comprising steps of: (a) the driving assisting device performing processes of (i) determining a gazing direction of a driver of a vehicle and (ii) identifying a location of a specific object and determining a distance between the specific object and the vehicle; and (b) the driving assisting device, on the condition that the location of the specific object is detected as being outside a virtual viewing frustum including a direct viewing frustum and an indirect viewing frustum, (i) if the distance between the specific object and the vehicle is determined as being less than a first predetermined distance, performs a process of increasing a threshold distance of a triggering condition for providing alarm, and (ii) if the distance between the specific object and the vehicle is determined as being less than a second predetermined distance, performs a process of providing alarm according to the threshold distance of the triggering conditions, wherein the first predetermined distance is numerically larger than the second predetermined distance and the second predetermined distance corresponds to the threshold distance of the triggering condition, and wherein the virtual viewing frustum includes (i) a direct virtual viewing frustum corresponding to the gazing direction of the driver of the vehicle and (ii) an indirect virtual viewing frustum corresponding to an indirect line of sight of the driver which is generated by any reflection component of the vehicle. (a) the driving assisting device performing processes of (i) determining a gazing direction of a driver of a vehicle and (ii) identifying a location of a specific object and determining a distance between the specific object and the vehicle; and (b) the driving assisting device, on the condition that the location of the specific object is detected as being outside a virtual viewing frustum including a direct viewing frustum and an indirect viewing frustum, (i) if the distance between the specific object and the vehicle is determined as being less than a first predetermined distance, performs a process of increasing a threshold distance of a triggering condition for providing alarm, and (ii) if the distance between the specific object and the vehicle is determined as being less than a second predetermined distance, performs a process of providing alarm according to the threshold distance of the triggering conditions, wherein the first predetermined distance is numerically larger than the second predetermined distance and the second predetermined distance corresponds to the threshold distance of the triggering condition, and wherein the virtual viewing frustum includes (i) a direct virtual viewing frustum corresponding to the gazing direction of the driver of the vehicle and (ii) an indirect virtual viewing frustum corresponding to an indirect line of sight of the driver which is generated by any reflection component of the vehicle. (i) if the distance between the specific object and the vehicle is determined as being less than a first predetermined distance, performs a process of increasing a threshold distance of a triggering condition for providing alarm, and (ii) if the distance between the specific object and the vehicle is determined as being less than a second predetermined distance, performs a process of providing alarm according to the threshold distance of the triggering conditions, wherein the first predetermined distance is numerically larger than the second predetermined distance and the second predetermined distance corresponds to the threshold distance of the triggering condition, and