To prevent elongated crushed matter from passing through a grate in an impact type horizontal crusher.

In a crusher, a material to be crushed is subjected to impact pulverization by the impact elements 4 of a rotor 3 and the crushed material is discharged through the opening part 21 of a grate 8. The ridges 16 at a position lowered from the top surface of the grate by a constant length are provided to the side surface faced with the opening part 21 of the grate 8 in the rotary direction of the rotor 3 and the shelf surfaces 10 comprising the top surfaces of the ridges 16 are formed over the total length in the axial direction of the rotor 3 of the side surface. In a reversible type, the shelf surfaces 10 are formed to both side surfaces of the opening part 21. If there are the shell surfaces 10, elongated crushed matter comes into contact with the shelf surfaces 10 to be prevented from passing through the grate 18. Therefore, it is prevented that many large non-crushed matters are mixed with a product crushed into a constant particle size or less.