To provide a bearing device for a rotary shaft which can further restrain the damage to a sliding bearing, by determining the position of a parting surface of the sliding bearing taking into account the position of the maximum pressure of an oil film. A bearing device includes a pair of sliding bearings for rotatably bearing a crankshaft of an internal combustion engine, and an oil supply passage for supplying a lubricating oil into clearances between the crankshaft and the sliding bearings. The sliding bearings are each composed of bearing halves bisected at a parting surface located on a flat plane, substantially orthogonal to the direction of the maximum pressure of the oil films, formed of the lubricating oil in the clearances. The bearing device is applicable to an internal combustion engine including a cylinder having an inclined cylinder axis, which reduces the vibration and noise of the internal combustion engine arising from vibration of a crankshaft, without depending on the angle of inclination of the cylinder axis, and which restrains abrasion and damage of end portion main bearings. |