Power transmission of chainless type bicycle

A powertrain for the chainless bicycle is provided to prevent an accident that clothes or a body is injured by a chain and to remove inconvenience of the deviating of the chain while shifting to a high speed and a low speed without the chain. A powertrain for the chainless bicycle comprises as the follows. A first drive unit(110) is meshed with a pedal shaft. A reduction device(130) is connected with the first drive unit A second drive unit(150) is connected to the reduction device. A power transmission shaft(175), which is connected to the second drive unit at a right angle, transmits the driving force to a rear wheel. A driven roller gear set connected to the hub-spoke central part of the rear wheel drives the rear wheel. A clutch engages the first drive unit, the second drive unit and reduction device for selectively transmitting the power.