Abstract: A device for heating a press tool (4), which is mounted in a press (3) for manufacturing products wholly or partially of plastic or composite, consists of a core (1) of electric sheet steel, a coil arrangement (9, 10, 11) placed around the core (1), and a voltage source (12). The voltage source (12) is connected to the coil arrangement (9, 10, 11) for generating a magnetic field in and around the core (1). The core (1) has two poles (8a, 8b) which, between themselves, receive the press tool (4) and are displaceable in relation to one another for applying a press force to the press tool (4) and conduct the generated magnetic field into the press tool (4). A press (3) comprises such a heating device and is used in a manufacturing method where the press tool (4) is heated by the magnetic field supplied thereto.