[en] Following the scheme of a method proposed by Suda and Uchida to treat the evolving convective core of the massive main sequence star, we investigate the evolutionary character of the convective core in the early stages of the horizontal branch evolution. In spite of the different behaviour of the opacity, the situation is essentially identical with those in the early stages of the upper main sequence evolution. The chemically inhomogeneous zone resembling to the Sakashita and Hayashi's semiconvection zone will be formed and developed in these early stages. It has been shown that the early stages of the horizontal branch evolution would be characterized not by the overshooting from the convective core but by the formation of the Sakashita and Hayashi type inhomogeneous convection zone. (author)