The invention relates to a mould for golf ball cores, which comprises an upper mould and a lower mould, wherein the upper mould is provided with a plurality of upper arc grooves in rows, and the upper arc grooves are formed by concaving the lower end surface of the upper mould; the lower mould is provided with a plurality of lower arc grooves which correspond to the upper arc grooves and are formed by concaving the upper end surface of the lower mould; the lower end surface of the upper mould is butted with the upper end surface of the lower mould; the upper arc grooves and the lower arc grooves form a complete ball groove; and the concave-convex contact layers are respectively formed in the upper arc grooves. Thus, the golf ball cores can be stably engaged in the arc grooves through the concave-convex contact layers. During die sinking, all the molded golf ball cores can be uniformly concentrated at the upper mould or the lower mould, without causing the upper mould and the lower mould to have different numbers of golf ball cores respectively. Therefore, the subsequent operation can be carried out conveniently, and the work efficiency can be improved effectively.