Screen device, comprising - a screen roller which is rotatable about an axle; - a screen which can be rolled up onto and unrolled from this screen roller; - an interior space in which the screen roller is fittable in order to accommodate the latter in an installed position of the screen device; - a support element on an end side of the screen roller for fastening the screen roller in the interior space; - a fastening body which partly delimits the interior space, to which the support element is attachable via a fitting movement virtually perpendicular to the axle of the screen roller; - a first guide element and a second guide element on the fastening body, which are arranged substantially parallel to each other, between which the support element is retractable and extendable in order to guide the support element during the fitting movement; - at least one securing element for securing the support element during the fitting movement, wherein this securing element is provided on the support element so as to be movable between a first position, wherein, in the mounted position, the securing element prevents the support element from sliding out of the guide elements (3, 4) and a second position, wherein the support element is slidable into and out of the guide elements (3, 4); - one or more spring-mounted elements which force the securing element to its first position; characterized in that the securing element comprises a rigid base body which comprises a projecting rigid fitting element or a fitting space and in that the first guide element comprises a corresponding fitting space or a corresponding projecting rigid fitting element, so that, in the installed position with the securing element in its first position, the projecting rigid fitting element engages in the corresponding fitting space in order to secure the support element. - a screen roller which is rotatable about an axle; - a screen which can be rolled up onto and unrolled from this screen roller; - an interior space in which the screen roller is fittable in order to accommodate the latter in an installed position of the screen device; - a support element on an end side of the screen roller for fastening the screen roller in the interior space; - a fastening body which partly delimits the interior space, to which the support element is attachable via a fitting movement virtually perpendicular to the axle of the screen roller; - a first guide element and a second guide element on the fastening body, which are arranged substantially parallel to each other, between which the support element is retractable and extendable in order to guide the support element during the fitting movement; - at least one securing element for securing the support element during the fitting movement, wherein this securing element is provided on the support element so as to be movable between a first position, wherein, in the mounted position, the securing element prevents the support element from sliding out of the guide elements (3, 4) and a second position, wherein the support element is slidable into and out of the guide elements (3, 4); - one or more spring-mounted elements which force the securing element to its first position;