To provide a balancer-shaft-supporting bearing unit capable of protecting a roller bearing, by receiving an impact load acting on a driven gear of the balancer shaft from a driving gear of a crankshaft by a sliding contact part.

The balancer shaft 30, on which a driven gear 35 is arranged that meshes with a driving gear 11 provided on a crankshaft 10 of an internal combustion engine, is rotatably supported by a shaft-supporting portion 21 of a housing 20 via a roller bearing 40. Between the balancer shaft 30 and the housing 20, a load-receiving portion 50 that has a receiving face 51 that receives an impact load applied to the driven gear 35 within a range of elastic deflection of the balancer shaft 30 is provided at a position close to at least one side of the both axial end side portions of the driven gear 35.