An epicyclic reduction gear device includes a cylindrical housing (1), having an internal circumference equipped with at least a crown wheel (2), at least a first train-carrier (7) rotatable inside the housing (1) and supporting a first output shaft (13), at least a planetary first wheel set (3a, 3b, 3c), hinged on relative pins (6a, 6b, 6c) fixed at the first train-carrier (7) and provided with related toothed portions (9a, 9b, 9c) engaged with the crown wheel (2), and a solar gear wheel (4) which is integral with an input shaft (10) and which is engaging with the planetary wheels (3a, 3b, 3c). The reduction gear device (12) has at least a first idle gear wheel (5) which is pivoted on the first train-carrier (7) and which engages two wheels (3a, 3b) of the planetary wheels (3a, 3b, 3c) in order to allow force balancing.