To provide a tapered roller bearing capable of being used even in cold area and the like, preventing the temperature rise of a shaft so as to suppress a bearing gap from decreasing, thereby reducing a load onto a large collar part or the like, and to provide a tapered roller bearing assembly and a railroad vehicle driving apparatus.

This tapered roller bearing includes an inner ring 1, an outer ring 2, and a plurality of tapered rollers 3 interposed between these inner and outer rings 1, 2. The tapered roller bearings according to this example are used in a pair facing front to front. A contact length between a rolling contact surface 3a of the roller and an outer ring raceway surface 2a is larger than a contact length between a rolling contact surface 3a of the roller and an inner ring raceway surface 1a on the cross-section viewed in a plane including a bearing axis L1 of the bearing cutting through this tapered roller bearing.