A hybrid drive unit includes a power distribution mechanism for distributing a power from an engine to a first electric motor and to an output shaft; a transmission, which is arranged between the output shaft and a second electric motor in a manner to transmit a torque therebetween, and which is capable of setting an overdrive ratio where a speed of the output shaft is higher than that of a predetermined input element; and an engagement mechanism for connecting the engine selectively with the input element of the transmission, and for setting a speed change ratio of the transmission to the overdrive ratio. The hybrid drive unit is capable of setting an overdrive mode and is easy to be downsized.