An output apparatus comprises: a plurality of interface sections for inputting data which is supplied from an upper apparatus such as a host computer; an input buffer section to store the input data; an analyzing section for analyzing the input data and for forming predetermined image data; and an output section such as a laser beam printer or the like for outputting or printing the image data. The output apparatus further includes a judging section for judging whether the data inputted from which one of the plurality of interface sections should be deleted, a deleting section for deleting by a predetermined method the data of the input buffer section in which the data to be deleted has been stored, and a notifying section to notify the interface which is deleting at present to the operator. When the designated interface section differs from the interface section which is printing at present, it is judged that the data in the input buffer section should be deleted. When the designated interface section coincides with the interface section which is printing at present, the data in both of the input buffer section and the data storing section to store the image data is deleted.
