PURPOSE: To provide a document processor which can easily be handled even by an unexperienced user and which can smoothly be processed.

CONSTITUTION: At the time of outputting document data, CPU 2 checks that the processor 17 is connected to a system at an appropriate opportunity, reads information on a processing that the processor 17 can execute from the processor 17 and stores it in PMEM 3. At the time of outputting document data, document data is converted into the form of input data of the processor 17 when the processor 17 executes the possible processing based on the storage, and the processor 17 executes the processing. When the processing terminates, output data is read into PMEM 3, and it is outputted from a printer and CRT.