An improved device for gluing the end flap of a log and a gluing method which can be implemented in a machine for producing logs, in which the logs (14), which come from a re-reeling machine, are fed to a gluing device (11) comprising in succession a bottom unwinding roller (16) and a top feed belt (17), and, immediately downstream of the unwinding roller (16), at least one stretch of inclined surface (21), of a pre-set length, followed by a vacuum-suction roller (24), set on top of which is a top roller (25), and then by a glue dispenser (27), there being provided on top of the unwinding roller (16) a blower element (19) for blowing an end flap (29) of the log (14) and, underneath, a photo-electric cell (20) for detecting the end flap (29), in which the log fed to the unwinding roller (16) is set with a position of the free end staggered by an angle (α), which is a function of the diameter of the log and of the pre-set length of the stretch of inclined surface (21), in such a way that, when the log thus positioned rolls on the inclined surface, it sets itself on the suction roller (24), with the free portion of the end flap (29) set exactly corresponding to the area of contact with the suction roller (24).