A single crystal of diacetylene monomer, 1,6-di(N-carbazolyl)-2,4-hexadiyne (DCHD), is polymerized by photo-irradiation keeping the b-axis of polymer crystals parallel to that of monomer crystals on which some amount of stress is introduced in the lattice of polymer crystals. In the present study, morphological changes on the surfaces of DCHD polymer crystal were observed by atomic force microscopy in order to examine the relaxation mechanism of such stress. On polymerization, nodule-like structures were formed on the surface, aligning along the direction of nearly 60 degrees with respect to the b-axis of monomer crystal. The alignment of nodules is concluded to correspond to a mechanical slip direction in the monomer crystal.