Rotary tiller with variable speed is equipped with the option of variable-speed gearbox. The motion obtained from the power-take-off through the changeable speed of gears in gearbox makes it possible to use the rotational speed of the blades differently; in this way, an effective shredding and mixing operation is provided.By means of the metal plate which is placed in rear, it enables to re-shred the dashed soil and protect environment from the risk of harm.