A powertrain structure includes a drive shaft and a driven shaft disposed coaxially, with end surfaces opposed to each other, and a torque damper interposed between the shafts and having half bodies fitted to a shaft end parts of the drive and driven shafts, with the half bodies joined together by engagement of opposed, outer circumferential end surfaces thereof and a damper spring interposed therebetween such that it straddles drive-side and driven-side spring recesses respectively formed in the opposed surfaces of the half bodies. One of two fitting parts provided between the half bodies and the respective shafts has a smaller clearance and the other has an larger clearance in the radial direction of the shafts.