In this study, we propose a shoe-type walking assist device that can control the inversion/eversion angle of the subtalar joint during heel contact, with the aim of improving the long-term quality of life of both elderly people and young healthy people. The proposed device enables the heel mechanism to rotate dynamically in the frontal plane to lead the subtalar joint alignment to the neutral position when the heel contacts the ground. The effectiveness of the proposed mechanism was demonstrated by comparing the amount of lateral thrust (lateral sway) during stepping movements with and without the mechanism assist in 5 healthy male subjects wearing the device.