An address translator capable of reducing system loads in address translation and an overhead in switching between operating systems. A plurality of address translation buffers classifies and stores virtual addresses and real addresses based on a plurality of operating systems which is run by a processor. For example, the address translation buffers store the virtual addresses and the real addresses in correspondence with the operating systems. According to a running operating system, an address translation controller accesses a corresponding address translation buffer to translate virtual addresses to real addresses.