Apparatus for preventing successive jamming of copy sheets in copying apparatus of the type including a forwarding mechanism for moving a copy sheet along a running path through a treatment zone for forming a visible image on the copy sheets and a copy sheet feeding mechanism, the successive jamming prevention apparatus including one or more detecting members disposed at detecting points in the running path so that at least one of the detecting members will contact a copy sheet at any position in the running path, a switch having normally closed contacts opened in response to contact of any of the detecting members with a copy sheet to prevent actuation of the copy sheet feeding mechanism and normally open contacts closed in response to contact of any of the detecting members with a copy sheet to provide an alarm signal.