Abstract: A balancer shaft for use in a multicylinder engine comprises a balance weight part formed to be eccentric in relation to a rotation axis of the balancer shaft and disposed along the alignment of cylinders in a cylinder block, an elongated shaft part extending from the balance weight part along the alignment of cylinders, a driving device provided on an end portion of the elongated shaft part for transmitting the rotation of a crank shaft in the cylinder block to the balancer shaft, a first journal provided on the end portion of said elongated shaft part, a second journal provided on a central portion of the balance weight part, and a third journal provided on an end portion of the balance weight part. The first, second and third journals are supported respectively by first, second and third bearing portions provided in the cylinder block.