A transparent document securing device, using in a flatbed scanner, includes a securing frame. The securing frame comprises at least a securing cell, wherein the securing cell further includes a concave, a cover and a clip mechanism. The concave includes a least a first opening and an open slot. The cover includes at least a second opening. The securing device employs the cover to mount a transparent document in a concave. A user is therefore be able to place the securing device along with the transparent document in the document glass of a scanning system. By a predetermined mode, the scanning system is able to directly scan the transparent document; no need to preview the scanned image to adjust the scanning area. Thus, the time for scanning is saved. Further the fixed depth of the concave is utilized to proved a precise focus of the scanning system. The quality of the scanned image is therefore improved.