A device of the present invention is an exponential calculation device for calculating x^(a/b) (where a and b are each an integer constant) for a given input value of x. The device includes: an input control section for outputting a value of x', wherein x'=x when x≤A (where A is a threshold value within a variable range of x) and x'=x/2^b when x>A; a core section for outputting a value ofz'=x'^(a/b); and an output control section for outputting a value of z, wherein z=z' when x≤A and z=z'*2^a when x>A.