The present invention provides a key button structure, capable of easily and positively finding a targeted character in accordance with an entry mode preset by a user, comprises: a key top; a light shielding section, which is attached onto rear face of the key top and of which is formed by reversely printing characters assigned to a key button for each character type display area; key backlights, each of which is provided in a dome anchoring sheet for covering a metal dome, and are arranged so as to be divided into three types: key backlights for lighting a numeral display area, a kana character display area, and an alphabetical letter display area respectively. For example, with a numeral entry mode preset, only the key backlight for lighting the numeral display area is lighted, thus displaying only a required numeral bright in the number entry mode.