1. A character input device in a document data processing apparatus comprising: keyboard means having at least a plurality of character keys and a search key; text memory means for storing document data consisting of a plurality of words; character memory means, connected to said keyboard means for storing data of at least one character constituting a word; word search means, connected to said keyboard means and said text memory means, for searching a word previously stored in said text memory means upon detection of the operation of said search key of said keyboard means; comparison means, connected to said character memory means and said word search means, for comparing whether or not at least one character data stored in said character memory means coincides with at least one character of a word to be searched from among the plurality of words stored in the text memory means; and a central processing unit, connected between said keyboard means and said comparison means, including means for inputting a word in a predetermined store position in said text memory means, as based upon the comparison result from said comparison means for indicating coincidence.