A winding device with a planetary-roller tear-off mechanism (30) is disclosed, comprising a first winding roller (4) which is driven to rotate in a pre-determined direction and a plurality of core support plates (8) that are arranged at a predetermined distance below the first winding roller (4), wherein an interval between the core support plates (8) and the first winding roller (4) is defined as a curved channel (9). A web material is conveyed through the curved channel (9) to a winding zone (14) to be wound as a roll. The planetary-roller tear-off mechanism (30) includes a plurality of rotary arms (3) and a plurality of planetary rollers (6). Each rotary arm (3) is set at a predetermined location below the first winding roller (4), and having a driving end (31) and a free end (32). Each planetary roller (6) is rotatable, and mounted to the free end (32) of the respective rotary arm (3). When the free end (32) of the rotary arm (3) is driven to rotate to a position facing a circumferential surface (4b) of the first winding roller (4), the web material is subjected to a drag force acting thereon to break the web material.