Distillers dried grain (DDG) and makgeolli spent grain (MSG) are agricultural byproducts to produce alcoholic beverage. However, they are known to contain enough nutrients. Mealworm is a promising insect resource for an animal feed ingredient as well as alternative human food. With low cost, DDG and MSG were investigated as a feed ingredient for rearing high quality mealworms. DDG and MSG were mixed with wheat bran and compared to control feed (only wheat bran) for its effects on larval survivorship, larval weight, duration for developmental period, pupation rate, and pupal weight. When DDG added, larval survivorship was reduced to 50~70% compared to the control group. Larvae fed on DDG were heavier from third to sixth week. Especially, larvae with 50% DDG were 28% heavier than the control group at the third week. For the larval period, the 50% DDG group was 11% less than that for the control. The pupal weight for the 30% DDG group was 7% heavier than that for the control group. Pupation rates for all the DDG groups were higher than 90%. When compared to the control, larval survivorship for the 70% MSG group was low, but the 50% and 70% MSG groups were high during the seventh and eighth weeks because of delayed development. After the eighth week, larvae with 70% MSG showed the highest larval weight increase as 9~18% compared to the control group. Except 70% MSG group, all of MSG groups showed more than 90% pupation rates. We confirmed that adding 30~50% of DDG or MSG to conventional wheat bran have a strong potential to replace the conventional wheat bran insect feed for quality insect production.