An image forming system has an image forming device for forming an image on a recording material in accordance with a set width of the recording material, and an image heating member. A first detecting member which detects a temperature of a first region of the image heating member, the first region corresponding to an outside region of a contact area, the contact area being contactable with a recording material having the set width, a second detecting member which detects a temperature of a second region of the image heating member, the second region corresponding to an inside region of the contact area, a cooling portion cools the first region of the image heating member in accordance with an output of the first detecting member, and a notification portion notifies that the set width of the recording material is wrong in accordance with an output of the first detecting member and an output of the second detecting member.