A target detection system using an EHF radar and the image processing is disclosed, in which the processing time is shortened by mutually complementing the disadvantages of the EHF radar and the image processing thereby to improve the reliability. The system comprises a radar, an image acquisition unit and an image processing ECU. The microcomputer of the ECU specifies an image recognition area based on the power output from the radar, and carries out the image processing only within the specified recognition area for the image obtained from the image acquisition unit. By performing the image processing only for the area where a target is detected by the radar, the time required for image processing is shortened on the one hand and the erroneous detection of letters on the road surface or the like is eliminated.