Image reading device and image forming apparatus capable of allowing or disallowing conveyance of original document through curved conveyance path depending on length of original document

An image reading device comprising:

• a document tray;
• a linear conveyance path extending approximately linearly in which a plurality of conveyance rollers capable of conveying an original document are disposed at a predetermined first interval;
• a curved conveyance path in which a plurality of conveyance rollers capable of conveying an original document are disposed at a predetermined second interval longer than the first interval;
• a document conveyance device that pulls out the original document placed on the document tray from the document tray and conveys the pulled original document through one of the linear conveyance path and the curved conveyance path;
• a scanning device that reads an image of the original document being conveyed through the linear conveyance path and an image of the original document being conveyed through the curved conveyance path;
• a length detecting device that detects a length of the original document;
• an operation device that receives input of a user's instruction based on an operation of a user on the operation device;
• and
• a controller that includes a processor and accepts, through the operation device when the processor executes a control program, a first instruction for conveying the original document through the curved conveyance path, wherein upon acceptance of the first instruction, the controller allows the document conveyance device to convey the original document through the curved conveyance path when the length of the original document detected by the length detecting device is a value equal to or larger than the second interval or the controller disallows the document conveyance device to convey the original document through the curved conveyance path when the length of the original document detected by the length detecting device is a value smaller than the second interval.