This study was conducted to investigate the quality characteristics of muffins with added ultrafiltered (UF) sunmul powder. Muffins were prepared with four different levels of UF powder (0%, 3%, 5% and 7%) and the physicochemical properties were examined. The volume and specific volume were lower in muffins prepared with UF powder than the control. The incorporation of UF powder in muffin lowered the lightness values but increased the redness values. Rheology testing showed that hardness increased with increasing UF powder and gumminess and brittleness were the highest in the control group and decreased with increasing UF powder. Initial isoflavone content was 2.39$sim$5.57 mg%, and decreased to 1.81$sim$4.09 mg% after baking, resulting in 24$sim$37% reduction in muffin formulations. Scanning electron microscopy showed that the size of the air cells increased with increasing UF powder levels. In sensory evaluation, overall acceptability score was the highest in muffins with 3% added UF powder and no significant difference was observed between control and 7% addition. Therefore, muffins prepared with up to 7% addition of UF powder would be at least as acceptable as control muffins.