Texts including required message are entered with a small number of keys such as those of a cellular telephone. In this case. a conversion table is unnecessary and the number of key operations is reduced. The number of input characters or input character strings composed by sequentially selecting one from a plurality of alphabets distributed to sequentially entered keys is relevant to the number of operation keys (N) raised to the number of distributed character (M) power (=NM) including meaningless characters or character strings and, with respect to these, character conversion is executed by referring to a dictionary means, through the operation of the conversion/next candidate key. The dictionary means stores numeric strings and words of meaningful characters or character strings among the said characters and character strings.