An image processing device, comprising: a feature point detecting section which detects one or more feature point from an image; and a feature value calculating section which calculates a feature value of the feature point detected by the feature point detecting section, wherein the feature point detecting section comprises: a ternarizing section which sets a pixel of the image as a target pixel and inputs pixel values of the target pixel and surrounding pixels of the target pixel, the surrounding pixels lying on a circle around the target pixel, and which changes each of the pixel values of the surrounding pixels to one of three signal values based on whether (i) the pixel value of a surrounding pixel is higher than the pixel value of the target pixel by a first threshold or more, (ii) the pixel value of a surrounding pixel is lower than the pixel value of the target pixel by the first threshold or more, or (iii) a difference in the pixel value between the target pixel and a surrounding pixel is less than the first threshold, in which the three signal values represent that brightness of a surrounding pixel is brighter or darker than or similar to brightness of the target pixel; and a determining section that determines the target pixel as the feature point when the number of consecutive surrounding pixels having a same signal value representing brighter or darker determined by the ternarizing section among the surrounding pixels is equal to or greater than a second threshold, and wherein the feature value calculating section calculates feature value components of a plurality of directions from the target pixel as the feature value of the target pixel by using the signal values of surrounding pixels in the plurality of directions, in which each of the feature value components is one of the three signal values. a feature point detecting section which detects one or more feature point from an image; and a feature value calculating section which calculates a feature value of the feature point detected by the feature point detecting section, wherein the feature point detecting section comprises: a ternarizing section which sets a pixel of the image as a target pixel and inputs pixel values of the target pixel and surrounding pixels of the target pixel, the surrounding pixels lying on a circle around the target pixel, and which changes each of the pixel values of the surrounding pixels to one of three signal values based on whether (i) the pixel value of a surrounding pixel is higher than the pixel value of the target pixel by a first threshold or more, (ii) the pixel value of a surrounding pixel is lower than the pixel value of the target pixel by the first threshold or more, or (iii) a difference in the pixel value between the target pixel and a surrounding pixel is less than the first threshold, in which the three signal values represent that brightness of a surrounding pixel is brighter or darker than or similar to brightness of the target pixel; and a determining section that determines the target pixel as the feature point when the number of consecutive surrounding pixels having a same signal value representing brighter or darker determined by the ternarizing section among the surrounding pixels is equal to or greater than a second threshold, and a ternarizing section which sets a pixel of the image as a target pixel and inputs pixel values of the target pixel and surrounding pixels of the target pixel, the surrounding pixels lying on a circle around the target pixel, and which changes each of the pixel values of the surrounding pixels to one of three signal values based on whether (i) the pixel value of a surrounding pixel is higher than the pixel value of the target pixel by a first threshold or more, (ii) the pixel value of a surrounding pixel is lower than the pixel value of the target pixel by the first threshold or more, or (iii) a difference in the pixel value between the target pixel and a surrounding pixel is less than the first threshold, in which the three signal values represent that brightness of a surrounding pixel is brighter or darker than or similar to brightness of the target pixel; and a determining section that determines the target pixel as the feature point when the number of consecutive surrounding pixels having a same signal value representing brighter or darker determined by the ternarizing section among the surrounding pixels is equal to or greater than a second threshold, and wherein the feature value calculating section calculates feature value components of a plurality of directions from the target pixel as the feature value of the target pixel by using the signal values of surrounding pixels in the plurality of directions, in which each of the feature value components is one of the three signal values.