A first aspect of an oil distributing structure for an internal combustion engine includes a bearing support wall including a plurality of guide ribs which are radially mounted on a surface thereof. The guide ribs may be integrally formed, and extend around an upper half of the bearing, for collecting oil which is splashed onto, and flows down the wall surface. In a second aspect of an oil distributing structure for an internal combustion engine, a slanted edge portion, descending toward the bearing, is formed on the bearing support wall, and is disposed laterally of a lower portion of the bearing. The described structure is useful for collecting oil splashed onto a wall surface of a crankcase, and for supplying the collected oil to a bearing in an internal combustion engine of the type in which a crankshaft bearing is supplied with oil splashed from nearby gears.