An image collating device that collates a first image and a second image includes a frequency characteristic acquiring unit, a frequency characteristic synthesizing unit, and a determining unit. The frequency characteristic acquiring unit acquires a frequency characteristic of the first image and a frequency characteristic of the second image. The frequency characteristic synthesizing unit generates a synthesized frequency characteristic by synthesizing the frequency characteristic of the first image and the frequency characteristic of the second image. The determining unit calculates a score indicating a degree to which the synthesized frequency characteristic is a wave having a single period, and collates the first image and the second image based on the score.