The present invention provides an image detection device and an image detection method for efficiently detecting a specific image area existing within an image. The image detection device of the present invention first changes a size of an original image using an initial value of a scaling factor (enlargement/reduction ratio) against the original image and detects the specific image (e.g. number plate). Next, the image detection device carries out the change of the original image size and the detection of the specific image repeatedly by changing the scaling factor. Further, an embodiment of the present invention realizes a high speed by repeating the detection while using the enlarged or reduced images, and also realizes the high speed by determining an area where another specific image cannot exist and carrying out the detection efficiently using this information.