Provided is a hybrid drive device which can set the OD mode and easily reduce its size. The hybrid drive device includes: a power distribution mechanism (4) for distributing the power outputted from an internal combustion engine (1) to a first motor (2) and an output shaft (5); and a transmission mechanism (6) arranged between the output shaft (5) and a second motor (3) in such a manner that torque can be transmitted and capable of setting an overdrive transmission ratio at which the rpm of the output shaft (5) is high for the rpm of a predetermined input element. The hybrid drive device further includes a coupling mechanism Cod, Bhi for selectively coupling the internal combustion engine (1) to the input element in the transmission mechanism (6) and setting the transmission mechanism (6) to the overdrive transmission ratio.