To automatically carry out test printing at appropriate timing without putting loads on the side of a host device by discriminating the form of each page from printing data, and comparing continuous form of each page, and also test printing a page being different from the previous page in form.

At first, an input I/F device 101 operates to communicate with a host device 20 so as to receive printing information, and convert it into an intermediate data to then be accumulated in an ancillary storing device 102. In the next place, it reads intermediate data for one page from the ancillary storing device 102 in order to form printing attributes regarding each page before being registered in a printing attribute administration table 127a on RAM 107. Then, the form of each page is discriminated from data registered in the printing attribute administration table 107a, and further continuous form of each page is compared; finally, test printing is conducted in regard of an (N+1) page when the form of an N page is different from the form of the (N+1) page.