PURPOSE: To prevent seizure by forming a tilted surface which is recessed toward a cylinder-block, on the abutted surface of the bearing cap of a cylinder block bearing part, and by forming a tilted surface adjustable to the abutted surface, on the abutted surface of the bearing cap bearing part.

CONSTITUTION: A crank shaft 12 is fitted to the bearing part 15 of a cylinder block 11, and a bearing cap 13 is fitted to the cylinder block 11 by a bolt 14. A tilted surface which is recessed toward the cylinder block 11, is formed on the bearing cap abutted surface 16 of the cylinder block 11, and a tilted surface adjustable to the tilted surface 16 is formed on the bearing part abutted surface 13A of the bearing cap 13. The force generated by the fastening of the bolt 14 is decomposed by the tilted surface, and time force returning to the inside works in parallel to the tilted surface 16, and the contraction of the part A of the crank shaft 12 is reduced. The seizure of the bearing part can thus be surely prevented.