A variable-angle vortex generator (10) installed in an intake pipe (100) of an internal combustion engine includes a shaft seat (1), a plurality of vanes (2) and a position restoring mechanism (3). Each vane (2) is arranged radially with an interval apart from each other and pivotally coupled to the shaft seat (1) and each vane (2) has a movable end (21) at an edge of the vane (2). The position restoring mechanism (3) is installed at the shaft seat (1) and includes a synchronizing element (31) for connecting each movable end (21). Each vane (2) is pushed by a fluid to produce a swing movement and let the fluid in the intake pipe (100) form a smooth vortex.