Abstract: A method and an apparatus for breaking into parts of a certain size and screening a bulk material, in which the bulk material is fed onto a flat grid (49) made to vibrate, the type and intensity of this vibration being chosen in a manner such that the large lumps of at least one type of material which do not pass directly through the openings in the grid are broken on the said grid, as a result of the said vibration movement, into fragments having a size which permits these fragments to pass through the openings in the grid. Preferably the material passing through the grid is collected on at least one screen (58, 59, 60) which is made to vibrate together with the grid and the material moving over this screen which has not fallen through is conveyed through a reduction device at the discharge of the screen, which device is formed by at least one breaker roller (64) having a double action and which can be made to rotate.