Abstract: A walker is intended for use by a baby who is learning to walk. The walker has a base which is provided in the underside thereof with a plurality of skidproof structures. The bottom of each skidproof structure has a reference plane slightly higher than a wheel set which is fastened with the base and is composed of a universal wheel and a wheel seat assembly. The wheel seat assembly includes a one-way roller and a threaded rod for confining and locating the one-way roller such that the moving range of the walker can be controlled to ensure the baby against accidents.