PROBLEM TO BE SOLVED: To provide an apparatus for automatic control of exhaust gas pressure of an internal combustion engine, capable of narrowing and expanding an area of a passage of an exhaust pipe depending on a speed of a vehicle.SOLUTION: This apparatus for automatic control of exhaust gas pressure of an internal combustion engine, includes a guide part having an opening part opened to the front face and the rear face, and installed such that the guide part covers a side face installed with a weight blade from a body 10 over a space area where the weight blade moves inside a range wherein a pressure adjustment plate 27 rotates, wherein the weight blade includes a perpendicular plate 67 formed of a platy member having a plate-like shape when sectioned by a virtual plane perpendicular to a virtual straight line connecting between a lead-in port 11 and a lead-out port 13.