A process roller for receiving and guiding substrates in strip form in vacuum coating installations. The process roller comprises a heater located inside the process roller, in the form of an elongated radiant heater, and also a cylindrical lateral surface for receiving a substrate in strip form, the process roller being mounted rotatably about an axis of rotation in a vacuum process chamber. A particularly uniform temperature distribution can be achieved on the process roller's lateral surface by the process roller (2) being configured in a vacuum-tight manner, by the lateral surface (3) of the process roller (2) being connected in a vacuum-tight manner to two end caps (4, 5), which have a flattened, outwardly curved hemispherical form, by the interior space of the process roller (2) being connected to a vacuum connection (6), and by the radiant heater (8) extending into the region of the end caps (4, 5).