Flatfoot is a common foot disorder. Some modifications by orthotic shoes for the flatfoot have been prescribed, however their effectivenesses are not fully proven yet. We have tried to validate the effectivenesses of conventional orthotic shoes for the flatfoot patients. We assessed the static and dynamic pressure, dynamic pressure-time integral, and relative impulse with and without wearing orthotic shoes. Thirteen subjects with the flatfoot were included in this study. The results showed the positive effects of orthotic shoes for the subjects. Especially the dynamic pressure-time integral values revealed the significantly reduced values at the medial side of midfoot, which meant the functional improvement of flatfoot status. We have concluded that the use of conventional orthotic shoes for the flat foot patients would be effective for properly selected patients, if there is no other associated abnormality.