An internal combustion engine (1) is designed so that the center axis P of a cylinder (4) is offset relative to a main journal part (2a) of a crankshaft (2). A bearing cap (17) is designed so that the side toward the cylinder center axis from a main bearing part (18) is secured to a bulkhead (7) by two fastening bolts (24a, 24c) while the side away from the cylinder center axis from the main bearing part is secured to the bulkhead by one fastening bolt (24b) and that the bearing cap securing force on the side toward the cylinder center axis from the main bearing part (18) is greater than the bearing cap securing force on the side away from the cylinder center axis.