PURPOSE: To provide a jam treating device whereby a jam can be prevented from being generated again by forgetting to close a guide plate while facilitating its opening and closing for treating the jam.

CONSTITUTION: In a picture forming device in which transfer paper fed out from a paper feed part is fed to a developing device through a conveying route 1 to perform transcription in a transfer part thereafter to form a picture on the transfer paper by performing fixing in a fixing part, an openable/closable guide plate 2 is arranged in the paper feed part and on the conveying route 1, and a solenoid 3 for opening this guide plate is connected to this guide plate 2 to provide a guide plate closing mechanism 7 for closing the guide plate 2 and a jam detecting sensor 8 for detecting a jam approximating the guide plate 2.