To evade a bookbinding failure that cannot wrap a book paper bundle in case work to wrap the book paper bundle that bundles book paper with a cover.

In order to set a cover editing area CA of a cover C, an input of pieces of information about the length HL2 of a short side of the book sheets H, the length CL of a long side of the cover C, and the thickness W of a spine cover of the cover is received from a user. Discrimination is made based on the received information whether the length CL of the long side of the cover C is shorter than a value obtained by adding the thickness W of the spine cover to twice the length HL2 of the short side of the book sheets H. If the length CL of the long side of the cover C is shorter than the obtained value, an alert is issued to urge the user to change at least one of the pieces of information.