An improved object detection apparatus using an interface with which user can set an object detection area intuitively with simple operation. Apparatus includes imaging module imaging and outputting an imaged picture, three-dimensional position detection module detecting a three-dimensional position and outputting detected position information, input module allowing user to input data for setting a detection area and processing module conversion-processing and outputting the picture. Using detection area setting data inputted by user, detection area in the three-dimensional space is decided and whether the three-dimensional position detected by the position detection module exists inside or outside the detection area is judged. Picture outputted by the imaging module is subjected to conversion processing based on judgment result and detection area is clearly indicated in the picture.