1. A character image generating apparatus made to generate a character image to be displayed on a display unit on the basis of a vector font for generating the character image through the use of a character form base line formed by combining a plurality of linear elements, comprising: a plurality of types of partial basic line generating means each for generating a partial base line corresponding to each of said linear elements of said character form base line; a vector font data storing unit for storing vector font data to be used for the generation of said character image; a partial base line length calculating unit for calculating a line length of said partial base line of a character which is an object of display on the basis of said vector font data stored in said vector font data storing unit; a partial base line generating means selecting unit for selecting one of said plurality of types of partial base line generating means on the basis of threshold information set on the basis of a display performance of said display unit and a vision characteristic of the human being and said partial base line length calculated in said partial base line length calculating unit; a character form generating unit for generating said partial base line corresponding to each of said plurality of linear elements constituting said character form base line through the use of said partial base line generating means selected by said partial base line generating means selecting unit for generating a character form of said character image; and a character image generating unit for generating said character image on the basis of said character form generated by said character form generating unit.