A snow tiller for the preparation of a snow cover of ski runs, the snow tiller being configured to be advanced in a traveling direction and comprising: - a frame extending symmetrically on opposite sides of a longitudinal axis parallel to the traveling direction; - at least one tiller module coupled to the frame and comprising a shaft, which rotates around a rotation axis transversal to the longitudinal axis and is equipped with a plurality of tools configured to penetrate the snow cover; and a casing, which is arranged around the shaft and delimits a processing chamber in which the snow is processed; - a finisher, which comprises a flexible mat, which is configured to define a support area for the snow tiller on the snow cover and comprises an end coupled to the casing; and a pressure bar which extends transversely to the longitudinal axis, and is fixed to the flexible mat at a distance from the end coupled to the casing; and - at least one adjusting assembly connected to the pressure bar and to the frame and/or casing and configured to allow a free oscillation of the pressure bar around an axis parallel to the longitudinal axis of the snow tiller, and selectively adjust the distance between the pressure bar and the casing, such that the portion of flexible mat between the pressure bar and the casing can take on a plurality of configurations between an extended configuration, to be used in fresh snow conditions, and an arched configuration, with a concavity facing upwards, to increase the accumulation of snow in the processing chamber and the levelling of irregularities in the snow cover; wherein the at least one adjusting assembly comprises a crossbar, which extends transversely to the longitudinal axis, and is coupled to the pressure bar and, by means of a spherical joint, to the frame; wherein a plane on which the axis of rotation lies and passing through the spherical joint identifies a spatial region under the plane; the pressure bar and the end of the flexible mat coupled to the casing being arranged in said spatial region. - a frame extending symmetrically on opposite sides of a longitudinal axis parallel to the traveling direction; - at least one tiller module coupled to the frame and comprising a shaft, which rotates around a rotation axis transversal to the longitudinal axis and is equipped with a plurality of tools configured to penetrate the snow cover; and a casing, which is arranged around the shaft and delimits a processing chamber in which the snow is processed; - a finisher, which comprises a flexible mat, which is configured to define a support area for the snow tiller on the snow cover and comprises an end coupled to the casing; and a pressure bar which extends transversely to the longitudinal axis, and is fixed to the flexible mat at a distance from the end coupled to the casing; and - at least one adjusting assembly connected to the pressure bar and to the frame and/or casing and configured to allow a free oscillation of the pressure bar around an axis parallel to the longitudinal axis of the snow tiller, and selectively adjust the distance between the pressure bar and the casing, such that the portion of flexible mat between the pressure bar and the casing can take on a plurality of configurations between an extended configuration, to be used in fresh snow conditions, and an arched configuration, with a concavity facing upwards, to increase the accumulation of snow in the processing chamber and the levelling of irregularities in the snow cover; wherein the at least one adjusting assembly comprises a crossbar, which extends transversely to the longitudinal axis, and is coupled to the pressure bar and, by means of a spherical joint, to the frame; wherein a plane on which the axis of rotation lies and passing through the spherical joint identifies a spatial region under the plane; the pressure bar and the end of the flexible mat coupled to the casing being arranged in said spatial region.