PURPOSE: To obtain an address converter shortened at its processing time by collectively informing also plural address conversion information corresponding to the peripheral addresses of an address to be plotted together with address conversion information corresponding to the address concerned when the address mishits an address conversion buffer built in a memory management unit.

CONSTITUTION: When an address to be plotted by a graphics plotter 3 mishits the address conversion buffer built in the 1st memory management unit, the 1st management unit collectively informs also plural address conversion information corresponding to the peripheral addresses of the mishit address together with address conversion information corresponding to the mishit address. In addition, the 1st memory management unit registers the plural address conversion information in its built-in address conversion buffer.