The invention relates to a core box for manufacturing casting cores from a moulding material rigidified by supply of heat, including at least two core box parts, which together provide the shape of the casting cores to be manufactured and a heating device for heating the core box parts. The heating device has at least one oil line in thermal contact with at least one of the core box parts and connected to an oil supply feeding the oil line with a tempered oil for heating the core box parts. The invention divides at least one of the core box parts into a contour plate, providing the shape of the casting cores to be manufactured, and a heating plate connected to the contour plate, said heating plate extending flat over the contour plate and in which the oil line is provided.