1. A method of automatically completing a text input, the method comprising: receiving a first part of a text from a user through a text input device; recognizing a speech of the user, which corresponds to the text; and completing a remaining part of the text based on the first part of the text and the recognized speech wherein the recognizing comprises: applying a weighted value to each of a plurality of words forming the input first part of the text in proportion to an input order of the words; and recognizing the speech in consideration of the weighted values applied to the words.