Disclosed herein are an apparatus and method for calculating a multiplicative inverse. The apparatus for calculating a multiplicative inverse includes a data input unit for receiving input data, a multiplicative inverse calculation unit for dividing an input degree-8 finite field corresponding to the input data into two first degree-4 finite fields so as to perform Advanced Encryption Standard (AES) encryption on the input data, and for performing a multiplicative inverse calculation on the first degree-4 finite fields in consideration of a circuit depth value (T-Depth) and qubit consumption of quantum gates in a quantum circuit, and a data output unit for outputting result data obtained by performing the multiplicative inverse calculation.