A planet wheel shaft includes a bearing portion for acting as a slide-bearing in cooperation with a planet wheel of a planetary gear. On at least one axial region of the bearing portion, a cross-sectional shape deviates from a circular shape so that the bearing portion is thicker in a first direction than in a second direction perpendicular to the first direction. The deviation from the circular shape widens a wedge-shaped gap that is between the bearing portion and the planet wheel when there is load in the first direction. This facilitates oil supply to an area where hydrodynamic oil pressure is formed for carrying load in the first direction because the widening the wedge-shaped gap compensates for narrowing the gap due to ovalization of the planet wheel caused by load in the second direction.