An electropneumatic controller has an electropneumatic control unit on which is provided an expansion interface, on which an expansion module arrangement is fitted. In the expansion module arrangement there extends at least one expansion working channel which is connected to a main working output and which is fluidically connected to the control unit at the expansion interface for connection to control valve means. The control unit further contains control electronics for electrically controlling the control valve means. Also proposed is a process control device equipped with a controller of this type.