A linear-rotary actuator includes a base, a first linear motor, a second linear motor, a linear rail, and a ball screw. The first and second linear motors are disposed on the base and respectively have a coil assembly and a magnet backplane. The linear rail is located on the base. The ball screw includes a screw and a nut, wherein the screw is connected to the first linear motor, and the nut is connected to the second linear motor. When the screw and the nut are driven by the first and second linear motors to move along the linear rail in a synchronized manner, the linear-rotary actuator provides linear motion output. When the nut is driven by the second linear motor to move along the linear rail in an asynchronous manner with respect to the screw, the linear-rotary actuator provides rotary motion output.