The utility model provides a round steel rolling device which comprises a blooming mill, a circular hole rolling mill and a guiding groove connecting piece. A flat box pass, a square box pass, a deformation box pass and an ellipse pass are sequentially arranged on the blooming mill and used for rolling a rolled piece to be in a flat box shape, a square box shape, a deformation box shape and an ellipse shape. One or more circular passes are arranged on the circular hole rolling mill and used for rolling the ellipse rolled piece conveyed by the blooming mill to be circular. The guiding groove connecting piece is connected between the blooming mill and the circular hole rolling mill and used for conveying the ellipse rolled piece rolled through the blooming mill to an inlet of the circular pass of the circular hole rolling mill in an aligned mode. According to the unique pass design, the good reference is provided for round steel rolling through the various rolling mills, meanwhile, the potential of old equipment on the brink of elimination is brought into play to a larger extent, and economic and social benefits are remarkable.