The invention discloses a rear guide device for a seamless steel tube rolling mill and belongs to the technical field of a seamless steel tube rolling mill. The rear guide device mainly comprises a guide base, two side guide plates and a top guide plate, wherein the guide base is equipped with a V-shaped groove; the two side guide plates are respectively constrained and installed at the inner sides of the V-shaped groove; the top guide plate is fixedly arranged on a swing device for opening or closing the top guide plate; the swing device is connected with a power unit; and when the top guide plate is closed, the two side guide plates and the top guide plate form a guide channel. By the invention, the technical problems that a rear guide device is difficult to replace and the replacement efficiency is low when seamless steel tubes with different specifications are rolled, thus the rear guide device can be widely applied to the manufacturing of the seamless steel tubes.