1. An address translation apparatus comprising: entry storage means for storing a plurality of entries, each entry containing a virtual page number, a physical page number, and a process identifier which is composed of plural bits; comparison information storage means for storing comparison information which defines a method for comparing a process identifier possessed by a process that is currently executed, with the process identifier in each entry; process comparison means for comprising the process identifier possessed by the process that is currently executed, with the process identifier in the entry, on the basis of the comparison information; and entry retrieval means for retrieving, from the entry storage means, an entry including a virtual page number equal to a virtual page number supplied from the outside, and a process identifier which matches the process identifier of the currently executed process, according to the result of comparison by the process comparison means.