Succinic acid is an expensive and high industrial value organic acid that can be used in many industries such as food, cosmetics, chemistry. It can be produced by bacterial fermentation. When cellulose and xylan in the lignocellulosic biomass are hydrolyzed into glucose and xylose with pretreatment process, they can be used as a carbon source in fermentation. This study was designed for the production of succinic acid from pretreated corncob by Actinobacillus succinogenes ATCC-55618. Corncob was pre-treated by organasolv. The cellulose and xylan were hydrolyzed into monomers using commercial enzymes. The optimal enzyme dosages were sought at 50C and pH 5.2, under which conditions pretreated corncob was hydrolyzed for separate hydrolysis and fermentation (SHF). The same test was repeated at 37C and pH 6.8 to find the required enzyme dosages under the simultaneous saccharification and fermentation (SSF). The cellulose and xylan recoveries were 69.2% and 68.8% for SHF, 31.8 % and 41.4 % for SSF. The SHF was conducted using the enzymatic hydrolysate and succinic acid yield was 0.48 g succinic acid/g sugar. In the SSF, the pretreated corncob was used as the carbon source, the succinic acid yields were 0.75 g succinic acid/g sugar. This study shows that corncob treated with organosolv had a potential as carbon source for succinic acid production by A. succinogenes either via SHF or SSF. Although the conditions in the fermentation step were not optimum for the enzyme activity, the SSF was more successful than SHF considering the succinic acid yield on the carbohydrates.