To provide an audio signal quantization device in which an amount of arithmetical operation can be reduced. A 0.75-power computing apparatus includes: an inverse number computing unit; a first -0.5-power computing unit; a multiplication unit; a second -0.5-power computing unit; and a program storage medium that is connected to an outside, whereby a program stored in the program storage medium is executed to compute the 0.75-power in a quantization computing expression. The inverse number computing unit, the first -0.5-power computing unit, the multiplication unit, and the second -0.5-power computing unit operate in such a manner that a multiplication between an infinity and zero which leads its operation result to an indefinite value is inhibited.