A crusher rotor arrangement that comprises a crusher rotor that crushes material and a counter blade assembly arranged in cooperation therewith, whereby the crusher rotor comprises a crusher blade structure fastened to its circumference and extending in its axial direction, and the counter blade assembly comprises the actual counter blade structure that crushes and cuts material together with the crusher blade structure of the crusher rotor, and a spring structure (7, 9) of the counter blade structure, the counter blade structure and its body being divided in the axial direction of the crusher rotor into several portions each with their own spring means, whereby between the crusher rotor and counter blade assembly, on the reverse side of the counter blade structure in the rotation direction of the crusher rotor, a fixed guide is mounted in cooperation with the counter blade structure to divide the space between the counter blade assembly and crusher rotor into separate routes for the accepted and rejected material, characterised in that - the fixed guide is a member that extends in the axial direction of the crusher rotor and narrows in a wedge-like manner toward the counter blade structure, and the opening for rejected material between the fixed guide and counter blade structure is located between the highest point of the crusher rotor surface and the horizontal plane formed by the crusher rotor axle, and the fixed guide on the side of the path of the accepted material is connected to a set of screens arranged below the crusher rotor and surrounding it at an axial distance of the size of the crusher blade structure. - the fixed guide is a member taht extends in the axial direction of the crusher rotor and narrows in a wedge-like manner toward the counter blade structure, and - the portion of the counter blade structure in cooperation with the fixed guide is formed of a wedge-like extension of the body of the counter blade structure formed on the reverse side of the counter blade structure and, when the counter blade structure yields, the extension is arranged to turn in the manner of a pendulum together with the portion of the counter blade structure at that location and to open an opening or path for the rejected material. - the fixed guide is a member that extends in the axial direction of the crusher rotor and narrows in a wedge-like manner toward the counter blade structure, and the opening for rejected material between the fixed guide and counter blade structure is located between the highest point of the crusher rotor surface and the horizontal plane formed by the crusher rotor axle, and the fixed guide on the side of the path of the accepted material is connected to a set of screens arranged below the crusher rotor and surrounding it at an axial distance of the size of the crusher blade structure. - the fixed guide is a member taht extends in the axial direction of the crusher rotor and narrows in a wedge-like manner toward the counter blade structure, and - the portion of the counter blade structure in cooperation with the fixed guide is formed of a wedge-like extension of the body of the counter blade structure formed on the reverse side of the counter blade structure and, when the counter blade structure yields, the extension is arranged to turn in the manner of a pendulum together with the portion of the counter blade structure at that location and to open an opening or path for the rejected material.