A method and an apparatus for analyzing a twinned crystal can display three-dimensionally the real space unit lattice, the reciprocal space primitive lattices and the reciprocal lattice points of each component of the twinned crystal. Respective crystal orientation matrices of the plural components of the twinned crystal are obtained with the use of X-ray single crystal structure analytical equipment. The first computing means finds the real-space unit lattices of the plural components based on the crystal orientation matrices and creates display data for displaying them three-dimensionally with possible their rotation, scaling up and down and translation. The second computing means finds the reciprocal-space primitive lattices and creates display data for displaying them three-dimensionally. The third computing means creates display data for displaying three-dimensionally reciprocal lattice points causing X-ray diffraction with a distinction between the components of the twinned crystal.