In a speed change gear system (1) in accordance with the present invention for changing between forward movement and rearward movement of a vehicle and for changing a speed of the vehicle by selectively fixing sun gears, carriers and ring gears of a plurality of epicyclic gear devices with respective mating clutches (8, 14, 24, 28), a brake (29) is connected to an output shaft (21) of this speed change gear system (1) to share energy absorption of the respective clutches, and the hydraulic pressure for the brake (29) is controlled in accordance with a rotation rate of the output shaft (21). Therefore, these clutches (8,14,18,24,28) can be small-sized. When the brake (29) is released, a quantity of lubrication oil being supplied is reduced, and therefore the stirring resistance of the lubrication oil can be reduced, and the transmission efficiency can be satisfactory.