A first acquiring section acquires, at first timing after a print job is received and before a print instruction is given, first print data located at a reference location indicated by reference information of data included in the print job, and stores the first print data in a storage section. A second acquiring section acquires, at second timing when the print instruction is given, second print data located at the reference location. A difference determining section determines whether the second print data are different from the first print data. A necessity determining section determines whether the second print data are necessary, when the second print data are different from the first print data. A printing section prints the second print data when the second print data are necessary, and prints the first print data when the second print data are unnecessary.