Screen device, comprising - a screen roller; - a screen which can be rolled up and unrolled on this screen roller, - an end lath, which is fitted to a side of the screen opposite to the side where the screen is rolled up and unrolled; - a tensioning system to tension the screen in the roll-up and unrolling direction, comprising on each lateral side of the screen: i. a band wheel, which is arranged next to the screen roller; ii. a tensioning cord, which can be rolled up and unrolled on this band wheel; iii. on the side of the screen device away from the screen roller, a reversing wheel, via which the tensioning cord is turned; and comprising a spring system (18, 19) for keeping the tensioning cords under spring tension; wherein each tensioning cord, on its end away from the band wheel, is fastened to a respective end of the end lath, wherein the spring system (18, 19) comprises a first spring sub-system on a first lateral side of the screen, which first spring sub-system comprises at least one spring element for keeping the respective tensioning cord under tension, and a second spring sub-system, arranged separate from the first spring sub-system, on the second lateral side of the screen, which second spring sub-system comprises at least one spring element for keeping the respective tensioning cord under tension, and wherein the first spring sub-system comprises adjusting means (10, 11, 14, 13, 16) for adjusting the spring force of the spring element, characterized in that each spring sub-system (18, 19) comprises a first pivot arm, which is articulately fastened to a first fixed pivot pin, which is fixedly arranged in the screen device and is articulately fastened to a displaceable pivot pin arranged displaceably in the screen device, in that each spring sub-system (18, 19) comprises a second pivot arm, which is articulately fastened to the displaceable pivot pin and is articulately fastened to a second fixed pivot pin, which is fixedly arranged in the screen device, in that the first pivot arm comprises a first part-arm and a second part-arm, which, with the aid of the spring element, are arranged resiliently with respect to each other, so that the spring force of the spring element drives the part-arms (25, 26) apart, and in that around the displaceable pivot pin is fitted a guide wheel, via which the respective tensioning cord is turned. - a screen roller; - a screen which can be rolled up and unrolled on this screen roller, - an end lath, which is fitted to a side of the screen opposite to the side where the screen is rolled up and unrolled; - a tensioning system to tension the screen in the roll-up and unrolling direction, comprising on each lateral side of the screen: i. a band wheel, which is arranged next to the screen roller; ii. a tensioning cord, which can be rolled up and unrolled on this band wheel; iii. on the side of the screen device away from the screen roller, a reversing wheel, via which the tensioning cord is turned; and comprising a spring system (18, 19) for keeping the tensioning cords under spring tension; i. a band wheel, which is arranged next to the screen roller; ii. a tensioning cord, which can be rolled up and unrolled on this band wheel; iii. on the side of the screen device away from the screen roller, a reversing wheel, via which the tensioning cord is turned;