An image storage device according to an example of the invention comprising a first storage unit which stores first image, a second storage unit which stores second image to be determined whether the second image includes detection target data which is the similar to data included in the first image, parallel comparison units which perform a process of comparing pixel values between a frame of the first image and a frame of the second image, and determining, based on a comparison result between the frame of the first image and the frame of the second image, whether the detection target data is included in the second image in parallel, and a third storage unit which stores, when it is determined that the detection target data is included in the second image, the detection target data.