The method for solving an N-queen problem includes: an initialization step of generating a quantum substitution matrix state which is a superposition of qubit states satisfying a row condition and a column condition of the N-queen problem; an Oracle step of performing an operation of inverting a phase of at least one entire correct answer state that satisfies a diagonal condition of the N-queen problem in the quantum substitution matrix state; an amplification step of amplifying an amplitude of at least one entire correct answer state of which the phase is inverted; amplifying the amplitude of at least one entire correct answer state to correspond to a predetermined value by performing the Oracle step and the amplification step repeatedly at a predetermined number of times; and acquiring one first correct answer state among at least one entire correct answer state based on observation of a qubit state.