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 an even column portion of a 2n×2n block or an n×n block sharing inverse transform coefficients; and 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.