A measuring method includes the following. An image to be tested of an object to be tested with a first characteristic pattern is formed and is copied to form multiple images to be tested. The multiple images to be tested are superimposed to form a to-be-tested overlapped image which has the multiple first characteristic patterns. A reference image of a reference object with a second characteristic pattern is formed and is copied to form multiple reference images. The multiple reference images are superimposed to form a reference overlapped image which has the multiple second characteristic patterns. The to-be-tested overlapped image and the reference overlapped image are superimposed to generate a virtual moiré image having a moiré pattern different from the multiple first characteristic patterns and the multiple second characteristic patterns.