Adjustable screening device for a wood chipper for screening out chopped material of at least two mutually different sizes of chopped material, wherein the screening device comprises: - a frame having a plurality of first screen openings having a first screen opening size, said first screen openings being arranged in rows and columns on said frame, - a screen opening dividing means which is settable into a first state and a second state by means of an adjusting mechanism, wherein - in the first state, the first screen openings have the first screen opening size, so that chopped material up to a first chopped material size can be screened through the first screen openings, and wherein - in the second state, second screen openings have a second screen opening size, so that chopped material up to a second chopped material size can be screened through the second screen openings, the second screen opening size being smaller than the first screen opening size, characterized in that the screen opening dividing device comprises: - dividing elements, each dividing element being associated with a respective first screen opening, - rotary shafts having a longitudinal axis, to which rotary shafts the dividing elements are attached to, wherein a rotary shaft is associated with each row of first screen openings, and wherein each rotary shaft is rotatably supported on the frame about its respective longitudinal axis, - an adjustment mechanism which is arranged to reversibly set the screen opening dividing device into the first and into the second state (P1, P2) by rotating the rotary shafts and the dividing elements mounted thereon about the longitudinal axes of the rotary shafts, wherein in the first state of the screen opening dividing device, the dividing elements are arranged such that the first screen openings have the first screen opening size, so that chopped material up to the first chopped material size can be screened through the first screen openings, and wherein the screen opening dividing device can be moved from the first state to the second state by rotating the rotary shafts so that the dividing elements, when the second state is reached, are arranged in front of the respective first screen openings with the first screen opening size, that each first screen opening is divided by its correspondingly associated dividing element into at least two second screen openings, which second screen openings each have the second screen opening size, so that chopped material up to the second chopped material size can be screened through the second screen openings. - a frame having a plurality of first screen openings having a first screen opening size, said first screen openings being arranged in rows and columns on said frame, - a screen opening dividing means which is settable into a first state and a second state by means of an adjusting mechanism, wherein - in the first state, the first screen openings have the first screen opening size, so that chopped material up to a first chopped material size can be screened through the first screen openings, and wherein - in the second state, second screen openings have a second screen opening size, so that chopped material up to a second chopped material size can be screened through the second screen openings, the second screen opening size being smaller than the first screen opening size, - dividing elements, each dividing element being associated with a respective first screen opening, - rotary shafts having a longitudinal axis, to which rotary shafts the dividing elements are attached to, wherein a rotary shaft is associated with each row of first screen openings, and wherein each rotary shaft is rotatably supported on the frame about its respective longitudinal axis, - an adjustment mechanism which is arranged to reversibly set the screen opening dividing device into the first and into the second state (P1, P2) by rotating the rotary shafts and the dividing elements mounted thereon about the longitudinal axes of the rotary shafts, wherein in the first state of the screen opening dividing device, the dividing elements are arranged such that the first screen openings have the first screen opening size, so that chopped material up to the first chopped material size can be screened through the first screen openings, and wherein the screen opening dividing device can be moved from the first state to the second state by rotating the rotary shafts so that the dividing elements, when the second state is reached, are arranged in front of the respective first screen openings with the first screen opening size, that each first screen opening is divided by its correspondingly associated dividing element into at least two second screen openings, which second screen openings each have the second screen opening size, so that chopped material up to the second chopped material size can be screened through the second screen openings.