In order to provide a hybrid drive system that suppresses a useless change of a pump driving path and that has a high durability, a plurality of drive sources, an output mechanism that outputs rotational power to an outside on the basis of those operation states, a control device that controls the operation states of the drive sources, an oil pump, and a pump input selecting mechanism that causes the oil pump to be driven with one of a plurality of rotary shafts to which power from the corresponding drive sources is inputable, are included, and the control device controls the rotation speeds (V1, V2) of the plurality of rotary shafts to unequal speeds by controlling the operation state of one of the plurality of drive sources.