The effect of deformation on the transformation behavior in Ti-Ni alloy was studied. Coil spring of Ti-Ni alloy used as element of tilt plate type heat engine, was cyclically expanded and contracted by temperature difference. The Results obtained in this study are as follows. 1. By the cyclic deformation, M_s and A_f decreased with increasing the number of cycles, however, M_s remained constant. The cycling effect was caused by the generation of dislocation during cyclic deformation 2. The cycling effect (decrease of M_s and A_f) increased with the increase of the heat treatment temperature and deformation strain. When the cyclic deformation was conducted in the temperature range of B2↔R-phase, transformation temperature changed little. 3. That unrecovered strain appeared to be proportional to the amount of decrease of M_s and A_f confirmed that cycling effect was caused by introduction of dislocation during deformation.