Sheet processing device and image forming device provided with the same

A sheet processing device that binds sheets having different shapes and then folds the sheets, comprising:

• a receiving tray capable of accommodating therein a sheet having a protruding portion at a part thereof and a sheet not having the protruding portion in a mixed state;
• a regulating member that regulates a leading end of the sheet accommodated in the receiving tray;
• a first binding member that binds a sheet bundle regulated by the regulating member at a substantially center thereof in a sheet conveying direction with a staple needle;
• a folding section that folds the sheet bundle bound by the first binding member in two;
• a second binding member that applies a pressure from a thickness direction of the sheet bundle to deform and performs a pressure-bonding binding on protruding portions of the sheet bundle folded by the folding section on a fore edge side of the sheet bundle;
• a detection member that detects presence or absence of the protruding portion of the sheets to be conveyed to the receiving tray;
• and
• a controller that issues an alarm signal when the detection member detects the sheet having the protruding portion is not accommodated in the receiving tray in a mode in which the first binding member is configured to bind the mixed sheets and after the mixed sheets are folded, the second binding member is configured to bind the protruding portions of the resultant sheet bundle.