The aim of this study was to determine the optimum amount of waxy millet flour (WMF) to add to rice flour in the preparation of Sulgidduk (waxy millet rice cakes). According to the results, increasing the level of WMF in the formulation caused the moisture contents of samples to increase ($37.14{sim}38.81%$). The L-value decreased with increasing additions of WMF whereas the b-value increased and the a-value did not differ by the addition of the flour. According to the mechanical evaluation results, hardness increased with increasing amounts of added WMF. Adhesiveness, cohesiveness, gumminess, and brittleness did not differ significantly and springiness was highest at the 30% level of WMF. From the sensory evaluation results, the 30% WMF samples received the highest overall-acceptability scores. In conclusion, according to its sensory and mechanical qualities, the optimal Sulgidduk formulation consisted of 30% WMF added to rice flour.