PURPOSE: To obtain speed stages which are four forward stages and one backward stage and to reduce shock upon gear shift by comprising two first and second planetary gear groups which are coupled together by way of an input shaft and a friction element and which couple two constitutional elements each other, and a third planetary gear group coupled to the first and second planetary gear groups through the intermediary of two constitutional elements, and coupled to an output shaft.

CONSTITUTION: There are provided two first and second planetary gear groups 20, 22 which are coupled together by way of an input shaft 12 and a first clutch C1 and which couple two constitutional elements with each other, a third planetary gear group 26 which is coupled to the first and second planetary gear groups 20, 22 by means of two constitutional elements and coupled to an output shaft 14. With this arrangement, a gear train 10 for an automatic transmission can have speed stages which are five forward stages and one backward stage, and does not control the speed change of the three planetary gear groups 20, 22, 26, independently from each other. With this arrangement, it is possible to reduce shock upon speed change.