A screen device including first rigid units (24) which constitute an upper slide guide frame portion (15) and second rigid units (17) which constitute a lower slide guide frame portion (16). The upper slide guide frame portion and the lower slide guide frame portion are retractable into the interior of a screen mounting frame (10). Wall portions (18) of the first rigid units are fitted in between the side wall portions of the second rigid units, and the upper slide guide frame portion intersects the lower slide guide frame portion in the interior of the screen mounting frame. Connection of the first rigid units can be released at an arbitrary position in the interior of the screen mounting frame when adjusting the length of the screen device (1), and the upper slide guide frame portion can be taken out from the screen mounting frame, so that an adjustment of the length in the field of installation is facilitated.