A transmission for a motor , the transmission receiving a rotational force from a rotational shaft of a motor to perform an output to an output shaft through shifting, and outputting the rotational force only in one direction at different shifting ratios according to forward/reverse rotation directions of the rotational shaft of the motor , the transmission comprising: a driving shaft having one or more one-way clutch contact surfaces formed on an outer periphery of a certain region of the driving shaft ; a dual one-way clutch including a carrier for accommodating forward restrictors and reverse restrictors in both faces of the carrier , respectively, the forward and reverse restrictors , being radially equidistantly arranged with a predetermined phase angle difference, and a forward output ring and a reverse output ring disposed outside the forward restrictors and the reverse restrictors , respectively, to be selectively rotated according to a rotation direction of the driving shaft ; and a low-speed rotational force transmitting means and a high-speed rotational force transmitting means including a plurality of gears , , , engaged with one another, the low-speed rotational force transmitting means and the high-speed rotational force transmitting means receiving the rotational force independently from the forward output ring and the reverse output ring of the dual one-way clutch so as to rotate the output shaft with the shifting ratios though different paths, whereby the dual one-way clutch allows a reverse input in a direction opposite to a rotation direction of an output of the output shaft characterized in that the carrier of the dual one-way clutch has a flange-shaped extension formed between the forward output ring and the reverse output ring , elastic bodies for elastically supporting balls toward the forward output ring and the reverse output ring are accommodated in the extension , and grooves , are formed on the forward output ring and the reverse output ring , respectively, wherein each of the grooves . corresponds to the ball and extends along an outer periphery of the corresponding output ring , . a driving shaft having one or more one-way clutch contact surfaces formed on an outer periphery of a certain region of the driving shaft ; a dual one-way clutch including a carrier for accommodating forward restrictors and reverse restrictors in both faces of the carrier , respectively, the forward and reverse restrictors , being radially equidistantly arranged with a predetermined phase angle difference, and a forward output ring and a reverse output ring disposed outside the forward restrictors and the reverse restrictors , respectively, to be selectively rotated according to a rotation direction of the driving shaft ; and a low-speed rotational force transmitting means and a high-speed rotational force transmitting means including a plurality of gears , , , engaged with one another, the low-speed rotational force transmitting means and the high-speed rotational force transmitting means receiving the rotational force independently from the forward output ring and the reverse output ring of the dual one-way clutch so as to rotate the output shaft with the shifting ratios though different paths, whereby the dual one-way clutch allows a reverse input in a direction opposite to a rotation direction of an output of the output shaft characterized in that the carrier of the dual one-way clutch has a flange-shaped extension formed between the forward output ring and the reverse output ring , elastic bodies for elastically supporting balls toward the forward output ring and the reverse output ring are accommodated in the extension , and grooves , are formed on the forward output ring and the reverse output ring , respectively, wherein each of the grooves . corresponds to the ball and extends along an outer periphery of the corresponding output ring , . <EOS>