1. An inverse transformer capable of performing inverse transforms for a 2n×2n block and an n×n block (where n is a natural number) with a single module, the inverse transformer comprising: a first inverse transform unit configured to perform an inverse transform operation on one of an even column portion of a 2n×2n block and an n×n block sharing inverse transform coefficients; a second inverse transform unit configured to store coefficients according to a first input mode and a second input mode and configured to select coefficients according to input mode and multiply the selected coefficients with an input value to perform an inverse transform of an odd column portion of a 2n×2n block or an n×n block; and a butterfly operation module configured to perform a butterfly operation on output values outputted by the first inverse transform unit and the second inverse transform unit, wherein: the second inverse transform unit includes: a coefficient register configured to store an n number of coefficients for each of the first input mode and the second input mode; a switch configured to selectively output the n number of coefficients for the first input mode or the second input mode from the coefficient register according to input mode; an n number of array multipliers configured to multiply the n number of coefficients selectively outputted by the switch with the input value and output intermediate values at an n-th point; and an adder/subtractor unit configured to add or subtract the intermediate values an m number of times (where m is a natural number) to output a final inverse transform result, and the coefficient register, the switch, the array multipliers, and the adder/subtractor unit are included in a single module.