The utility model discloses a plastic extruding, rounding and granulating machine. The device comprises a boss, an extrusion device and a rounding device, the extrusion device comprises a rack mountedon the boss, an extrusion motor mounted on the rack, an extrusion cylinder mounted on one side of the rack, and an extrusion screw arranged in the extrusion cylinder; wherein the extrusion screw penetrates through the rolling cylinder and the rack and is connected with the extrusion motor, the rounding device comprises a base, a rounding motor arranged in the base, a rolling cylinder mounted at the top of the base and a friction disc mounted in the rolling cylinder, the friction disc is connected with the rounding motor through a coupler, a discharging hopper is arranged at the top of the rolling cylinder, and an outlet of the extrusion cylinder is located over the discharging hopper. The plastic granulator is simple and ingenious in structure and small in occupied area, plastic particlesextruded by the rolling cylinder directly fall into the rolling cylinder, the plastic particles are rounded by the friction disc, the granulation effect is improved, the granulation time is shortened, the labor cost is reduced, and the labor intensity is reduced.