1. A method for acquiring a comparative image of a measured image measured from a semiconductor device and a reference measured image measured from a reference semiconductor device, the method comprising: acquiring the measured image measured from the semiconductor device and a first pattern image showing a pattern of the semiconductor device corresponding to the measured image; acquiring the reference measured image measured from the reference semiconductor device being the semiconductor device or a semiconductor device different from the semiconductor device and a second pattern image showing a pattern of the reference semiconductor device corresponding to the reference measured image; acquiring matching information indicating a correlation of the first pattern image and the second pattern image based on the first pattern image and the second pattern image, wherein the matching information is obtained by adjusting an image size of at least either one of the first pattern image and the second pattern image based on a ratio of a first size of visual field indicating a range on the semiconductor device of the first pattern image to a second size of visual field indicating a range on the reference semiconductor device of the second pattern image; and determining a difference of the measured image and the reference measured image based on the matching information to acquire the comparative image.