The invention discloses a collecting device for triplicate invoices, belongs to the technical field of office automation equipment, and solves the technical problem that triplicate invoices cannot be automatically cut and collected by an existing invoice stamp machine. The collecting device for triplicate invoices comprises a rack, a first cutting knife, a second cutting knife, a third cutting knife, a second track capable of sliding along the rack up and down, and a second driving mechanism for driving the second track to move reciprocatingly up and down. One end of each of the first cutting knife, the second cutting knife and the third cutting knife is hinged to the rack. The other end of each of the first cutting knife, the second cutting knife and the third cutting knife is hinged to the second track. The second driving mechanism comprises a second driving motor, a second controller for controlling the second driving motor to discontinuously rotate, a second rotating disc coaxially connected to an output terminal of the second driving motor, and a second connecting rod with one end eccentrically hinged to the second rotating disc and the other end hinged to a second guide rail.