Abstract: A logarithmic graph plotting apparatus capable of easily setting and displaying x- and/or y-axes as logarithmic ones to thereby display a logarithmic graph. A graph range setting picture (View Window) is displayed by operating a “range” key. The x- and y-coordinate ranges are inputted and set on the graph range setting picture. Graph plot data (x1, y1) (x2, y2), (x3, y3), . . . , (xn, yn) corresponding to any particular graph function expression are calculated based upon the coordinate ranges to thereby plot and display a corresponding a graph in a coordinate system with the x- and y-coordinate axes. When logarithmic graph display check boxes ([ ]x-Log) and/or ([ ]y-Log) on the setting picture (View Window) are checked off, logarithmic scale lines corresponding to the set x- and y-coordinate ranges are set and plotted. In addition, each of the graph plot data (x1, y1) (x2, y2), (x3, y3), . . .