1. A method for recognizing characters in a portable terminal with a scan module, comprising the steps of: generating scanned image data corresponding to a scan target using the scan module; measuring a current moving speed of the portable terminal while the portable terminal moves across the scan target; deleting part of the scanned image data when the current moving speed is less than a lower limit of an optimal scan speed range, and performing character recognition on remaining scanned image data; and detecting image data most similar to the scanned image data from a correction image database when the current moving speed is greater than an upper limit of the optimal scan speed range, and outputting characters corresponding to the detected image data as character recognition results, wherein the correction image database is an aggregate of image data generated by scanning that is performed when the portable terminal moves at a moving speed greater than or equal to the upper limit of the optimal scan speed range.