A target detection system for a vehicle, the system comprising: a detection sensor detecting a target based on a wave reflected from the target; a camera sensor monitoring the target based on an image including the target; and a controller determining a first risk level of the target based on data acquired through the detection sensor including a change in a speed of the target in a transverse direction of the vehicle, determining a second risk level of the target based on data acquired through the camera sensor, and computing a final risk level based on both the first risk level and the second risk level, wherein the controller computes a time-to-collision and an impact point, as factors for determining the first risk level, wherein, in a case where the change in the speed in the transverse direction occurs, the controller recomputes the time-to-collision and the impact point by adding the change in the speed in the transverse direction to values, respectively, that result from computing the time-to-collision and the impact point, wherein the first risk level is determined to indicate either risk or safety, wherein, in a case where the recomputed time-to-collision is shorter than a first threshold value and where the recomputed impact point falls within a second threshold value, the controller determines the first risk level as indicating the risk, wherein the second risk level is determined to indicate either risk or safety, wherein the controller extracts left and right sides of the image obtained by the camera sensor through monitoring, as a warning region, wherein, in a case where the target is present in the warning region, the controller determines the second risk level as indicating the risk, wherein, in a case where the first risk level and the second risk level both indicate the risk, the controller determines the final risk level as indicating the risk, wherein, in a case where the first risk level and the second risk level both indicate the safety, the controller determines the final risk level as indicating the safety, wherein, in a case where only one of the first risk level and the second risk level indicates the risk, the controller determines the final risk level as pending in which the controller delays generation of a warning, and, when the generation of the warning is delayed for a predetermined time or longer, generates the warning. a detection sensor detecting a target based on a wave reflected from the target; a camera sensor monitoring the target based on an image including the target; and a controller determining a first risk level of the target based on data acquired through the detection sensor including a change in a speed of the target in a transverse direction of the vehicle, determining a second risk level of the target based on data acquired through the camera sensor, and computing a final risk level based on both the first risk level and the second risk level, wherein the controller computes a time-to-collision and an impact point, as factors for determining the first risk level, wherein, in a case where the change in the speed in the transverse direction occurs, the controller recomputes the time-to-collision and the impact point by adding the change in the speed in the transverse direction to values, respectively, that result from computing the time-to-collision and the impact point, wherein the first risk level is determined to indicate either risk or safety, wherein, in a case where the recomputed time-to-collision is shorter than a first threshold value and where the recomputed impact point falls within a second threshold value, the controller determines the first risk level as indicating the risk, wherein the second risk level is determined to indicate either risk or safety, wherein the controller extracts left and right sides of the image obtained by the camera sensor through monitoring, as a warning region, wherein, in a case where the target is present in the warning region, the controller determines the second risk level as indicating the risk, wherein, in a case where the first risk level and the second risk level both indicate the risk, the controller determines the final risk level as indicating the risk, wherein, in a case where the first risk level and the second risk level both indicate the safety, the controller determines the final risk level as indicating the safety, wherein, in a case where only one of the first risk level and the second risk level indicates the risk, the controller determines the final risk level as pending in which the controller delays generation of a warning, and, when the generation of the warning is delayed for a predetermined time or longer, generates the warning.