A power take-off device (10) connectable to a tractor provided with a power take-off, which comprises a support frame (11) fixable to a tractor and suitable for rotatably supporting at least an input shaft (21) suitable for taking drive from the tractor power take-off and at least an output shaft (22) suitable for activating at least a work tool, at least a second output shaft (40, 60) being provided, parallel to the first output shaft (22) and suitable for activating at least a further work tool, and drive transmission means (24-27, 40,41,51,52, 61,62,71,72) interposed between the input shaft (21) and the second output shaft (40, 60), wherein the transmission means comprise at least a drive pulley (24-27) keyed on the input shaft (21) and at least a driven pulley (41,42,61,62), characterised by comprising at least a pair of the drive pulleys (24,2526,27) connected, by means of respective flexible organs (51,5271,72) to a respective pair of the driven pulleys (41,4261,62), the driven pulleys (41,4261,62) of the pair being made selectively solid in rotation with the second output shaft (40, 60) via selection means (43,63).
