An engine (E) has two balancer shafts (21,22) supported on two bearing bushings (52a,52b) which are made of the same material and mounted to a balancer holder. Lubricating oil passages (293,294,295) for supplying oil to the bearing bushings are defined offset upwards from the centers O of the bearing bushings (52) and by a distance δ. Each of the bearing bushings has two oil bores (52a1,52b2) having a center angle θ other than 180°. The two oil bores in the bearing bushing of one balancer shaft communicate with the lubricating oil passages, and one of the oil bores in the bearing bushing of another balancer shaft communicates with the lubricating oil passage, while the other oil bore of that another balancer shaft is closed to keep out of the lubricating oil passage. Thus, downstream ends of the lubricating oil passages for supplying the oil to the bearing bushings of the plurality of rotary shafts can be closed without use of a special closing member such as a blind plug.