The invention relates to the field of printers, in particular to a paper feeding mechanism for an invoice printer. The paper feeding mechanism comprises a fixed base, a printer main body, a paper feeding hole, a paper discharging hole, a flow guide plate, a driving mechanism, an extrusion mechanism, a paper suction mechanism and a storage mechanism, the printer main body is fixedly connected to the upper end of the fixed base, and the paper feeding hole is formed in the upper end of the printer main body. A driving rotating shaft of the driving mechanism rotates to drive a paper suction rotating roller of the paper suction mechanism to rotate, a piston plate can slide in an air cavity through extrusion of a pull rod by an arc-shaped top plate, finally, an air pressure suction head sucks invoice paper to slide out of a front baffle of the storage mechanism, and the air pressure suction head is disconnected with the arc-shaped top plate through the pull rod, the air pressure suction headis disconnected from the invoice paper and enters the printer main body for printing, full-automatic paper feeding of the printer is achieved, the troublesome operation that invoices are manually fedto designated positions of the printer one by one is avoided, and the printing efficiency is improved.