The present invention discloses a watertight monitoring device and comprises: fixing frame, a watertight cover, an image-capturing module, an upper cover, at least an adjustment tab, at least a plastic film, a front cover, and a rear cover; wherein the fixing frame has an outer surface provided with a recess having at least a through hole, the plastic film having an end coupled with the bottom edge of the adjustment tab and an opposite end passing sequentially through the aperture of the watertight cover and the through hole of the recess on the outer surface of the fixing frame and coupled with the adjustment rod of the image-capturing module, wherein the projecting portion of the adjustment tab can be pushed along the outer surface of the monitoring device so that the adjustment tab is moved in the arc direction, and the plastic film thus driving the adjustment rod of the image-capturing module so as to adjust functions of the image-capturing module.