To miniaturize an engine, and to increase its output by reducing the influence on a thrust surface by the axial force of a cap bolt to prevent degradation in flatness and perpendicularity of the thrust surface.

The diameter of a cap bolt to fix a bearing cap to a bulkhead 1 to which a thrust metal is fitted is reduced, and the diameter of a cap bolt hole 5 is reduced. At the same time, the diameter of a counter bore 6 provided on an opening part side of the cap bolt hole 5 is reduced. The counter bore 6 is provided deep so that its terminating end part 7 is not overlapped on a thrust metal fitting surface 8. In addition, a communication hole 9 is arranged so that a part of the communication hole is present between a screw part of the cap bolt hole 5 and the thrust metal fitting surface 8. The rigidity around the counter bore 6 is increased, and the influence of the axial force is dispersed. The action to draw the thrust metal fitting surface 8 in the tightening direction by the axial force is shut off.