A rectangular substrate is prepared by providing a starting rectangular substrate having front and back surfaces and four side surfaces as ground, and pressing a rotary polishing pad perpendicularly against one side surface under a constant pressure, and relatively moving the rotary polishing pad and the substrate parallel to the side surface, for thereby polishing the side surface of the substrate. In the imprint lithography, the rectangular substrate is capable of controlling compression and pattern shape at a high accuracy and thus transferring a complex pattern of fine feature size to a recipient.