An image processing apparatus includes a reception unit, an acquisition unit, an enlarging/reducing unit, and a detector. The reception unit receives two image data to be compared. The acquisition unit acquires character sizes of characters contained in the two image data received by the reception unit. The enlarging/reducing unit enlarges or reduces the image data received by the reception unit such that the character sizes of the characters contained in the two image data acquired by the acquisition unit coincide with each other. The detector detects a difference between the two image data which have been enlarged or reduced by the enlarging/reducing unit such that the character sizes of the characters contained in the two image data coincide with each other.