A hybrid vehicle transmission includes input and output shafts, first and second motor/generators, a first planetary gear train in which one rotary element of three rotary elements is connected to the input shaft and another thereof is connected to the first motor/generator, a second planetary gear train in which one of three rotary elements is connected to the output shaft and another thereof is connected to the second motor/generator, a first external gear pair consisting of a first gear, connected to a remaining rotary element of the first planetary gear train, and a second gear, connected to a remaining rotary element of the second planetary gear train, and a second external gear pair consisting of a third gear, connected to the input shaft, and a fourth gear directly connected to one rotary element of the second planetary gear train.