The invention relates to a feeding device of a bag making machine. The feeding device comprises a support, a pair of rubber rollers are installed on the support, and a rubber roller shaft of one rubber roller is in transmission connection with a rubber roller driving motor installed on the support through a belt synchronizing mechanism. The feeding device is characterized in that the back end of the support is hinged to the vertex angle of a triangular support through a triangular support driving shaft, the bottom edge of the triangular support is a straight-plate-shaped track, and a stopping hook and a hook are arranged at the upper end and the lower end of the track respectively. The triangular support driving shaft is in rotation connection with the support and is fixedly connected with the triangular support, one end of the triangular support driving shaft is in transmission connection with a triangular support driving motor installed on the support through a gear transmission mechanism; two sliding wheels correspondingly matched with the track are installed on a raw material shaft. The feeding device has the advantages that labor is saved during material loading, the energy consumption is low, the energy resource and the production cost are saved, and the structure is simplified.