A power train prevents the decrease in the power efficiency accompanied by the converting process between the kinetic energy and the electrical energy due to the large energy flow through the electrical path when the motor generator serves as a transmission and thus prevents the increase in the capacity of the motor generator and the bad fuel economy. The power train for a hybrid electric vehicle includes an engine, first and second motor generator, a battery, a plurality of planetary gear sets, and a plurality of breaks. The plurality of planetary gear sets convert the driving forces output from the engine, and the first and second motor generators to have an appropriate gear ratio according to a driving state and output the converted driving forces to a driving shaft. The plurality of breaks are provided in the plurality of planetary gear sets and control the output revolution on the basis of the gear ratio determined according to a driving state.