A hybrid driving unit, comprising: an input shaft for inputting motive power from an internal combustion engine; an output shaft disposed on an axis in line with said input shaft and interlocking with driving wheels; a first electric motor disposed on said axis and having a stator and a rotor; a power splitting planetary gear disposed on said axis and having a first rotary element coupled with said input shaft, a second rotary element coupled with said rotor of said first electric motor and a third rotary element coupled with said output shaft; a second electric motor disposed on said axis and having a stator and a rotor; and a transmission disposed on said axis and shifting and transmitting revolution of said rotor of said second electric motor to said output shaft; and said hybrid driving unit being characterized in that: said first electric motor, said power splitting planetary gear, said second electric motor and said transmission are stored in a casing member while said power splitting gear, said first electric motor, said transmission and said second electric motor are disposed on said axis in this order from the foremost part to the rearmost part; said stators (24, 28) of said first and second electric motors (20, 23) are fixed to said casing member; said casing member is provided, at the front end thereof, with a coupling section which can be fixed to said internal combustion engine and at the rear end thereof, with a mounting section which can be supported by a body; said output shaft is composed of a front end coupling section, an intermediate coupling section, and a rear end coupling section formed in a body; and said third rotating element of said power splitting planetary gear is coupled to said front end coupling section and a sun gear of said transmission is relatively and rotatably supported by said intermediate coupling section through an intermediary of bearings (1, m) fitted to an outer peripheral face of said intermediate coupling section. an input shaft for inputting motive power from an internal combustion engine; an output shaft disposed on an axis in line with said input shaft and interlocking with driving wheels; a first electric motor disposed on said axis and having a stator and a rotor; a power splitting planetary gear disposed on said axis and having a first rotary element coupled with said input shaft, a second rotary element coupled with said rotor of said first electric motor and a third rotary element coupled with said output shaft; a second electric motor disposed on said axis and having a stator and a rotor; and a transmission disposed on said axis and shifting and transmitting revolution of said rotor of said second electric motor to said output shaft; and said first electric motor, said power splitting planetary gear, said second electric motor and said transmission are stored in a casing member while said power splitting gear, said first electric motor, said transmission and said second electric motor are disposed on said axis in this order from the foremost part to the rearmost part; said stators (24, 28) of said first and second electric motors (20, 23) are fixed to said casing member; said casing member is provided, at the front end thereof, with a coupling section which can be fixed to said internal combustion engine and at the rear end thereof, with a mounting section which can be supported by a body; said output shaft is composed of a front end coupling section, an intermediate coupling section, and a rear end coupling section formed in a body; and said third rotating element of said power splitting planetary gear is coupled to said front end coupling section and a sun gear of said transmission is relatively and rotatably supported by said intermediate coupling section through an intermediary of bearings (1, m) fitted to an outer peripheral face of said intermediate coupling section.