An internal combustion engine comprises a cylinder block having a plurality of main bearing bulkheads, and a skirt section. Each bearing bulkhead is formed with through-holes each of which as an upper end opening to the skirt section and a lower end opening to the bottom surface of the bearing bulkhead. The bearing bulkhead is formed at its bottom surface with a depression. Each of a plurality of bearing caps is installed to the bearing bulkhead in a manner to fit in the bearing bulkhead depression. Additionally, bolts are disposed respectively in the bearing bulkhead through-holes, each bolt having an upper end section located on the skirt section and a lower end section located in the hole formed in the bearing cap, thereby eliminating the need for excess structure on the bearing cap to sharply reduce the weight of the bearing cap.