A data rewriting apparatus for a photographic camera, which comprises a film speed reading unit for automatically reading the film speed recorded on a container of a film in use; a first memory including RAM for the storage of the film speed; a second memory including E.sup.2 PROM for the storage of the film speed; a rewriting unit for rewriting a value stored in the first memory to a value stored in the second memory; a comparator for comparing the value stored in the second memory with that stored in the first memory; and a rewrite control unit for inhibiting the rewriting of the second rewriting unit when the comparator indicates that the value stored in the second memory is identical with that stored in the first memory.