A multi-stage transmission for vehicles includes an input shaft for receiving power from an engine; an output shaft for outputting the power; and a first, a second, a third, and a fourth planetary gear device. Each of the planetary gear devices has three rotary elements. The transmission further includes a first rotary shaft connected to the input shaft; a second rotary shaft; a third rotary shaft; a fourth rotary shaft; a fifth rotary shaft; a sixth rotary shaft; a seventh rotary shaft connected to a first rotary element of the third planetary gear device; and an eighth rotary shaft connected to a third rotary element of the fourth planetary gear device and to the output shaft.