To provide a method for more efficiently calculating a mathematical function at a higher speed.

An inputted number is inputted to a lookup table. The lookup table supplies three coefficients on the basis of bits included in an input for regulating a series of bins. The 1st coefficient is directly inputted to an adder for generating an output. The 2nd coefficient is multiplied by a number corresponding to the distance of the input from the edge of the bins. The multiplied number is inputted to the adder generating the output. The 3rd coefficient is multiplied by a number to be a result obtained by inputting the number corresponding to the distance of the input from the center of the bin to a curve- fit function. The multiplied result is inputted to the adder generating the output. These three addends are positioned and summarized and an output corresponding to a certain selected mathematical function in the summarized input within a range of a certain accuracy is generated.