A memory address generating apparatus comprising an address converting circuit, after setting a first setting region storing substitution source data and a second setting region storing substitution destination data that are a substitution target of the substitution source data in an address space provided by the memory, if a specified address specified by the processor as the access destination to the memory is included between a first beginning address and an end address of the first setting region, changing the specified address to a substitution destination address generated by adding a difference between the specified address and the first beginning address to a second beginning address of the second setting region.