1. A map symbol drawing device comprising: a texture generating unit for generating one or more textures within limits of a maximum size in a memory which can be used as textures; a number-of-references counting unit for counting a number of references per symbol type to symbols existing in a map; a symbol image writing unit for acquiring images of a number of symbols having a larger number of references per symbol type which is counted by said number-of-references counting unit from among the symbols existing in said map to write the image of each of the number of symbols having a larger number of references in a texture generated by said texture generating unit; a symbol information storage unit for storing symbol information showing a type and a write position of each of the symbols whose images are written in the texture by said symbol image writing unit; a polygon generating unit for generating vertices of a 3D polygon according to display coordinates of a symbol to be drawn; a write checking unit for referring to the symbol information stored in said symbol information storage unit to check to see whether or not an image of a symbol of same type as the symbol to be drawn is written in the texture; a texture coordinate setting unit for, when said write checking unit determines that an image of a symbol of same type as the symbol to be drawn is written in the texture, setting the write position of said symbol in said texture to the vertices of the 3D polygon generated by said polygon generating unit as texture coordinates, otherwise generating an original texture in which the image of the symbol to be drawn is drawn and setting coordinates of said texture to the vertices of the 3D polygon generated by said polygon generating unit; and a polygon drawing unit for drawing the 3D polygon in which the texture coordinates are set by said texture coordinate setting unit.