A bearing device includes: a journal part, a main bearing, a cylinder block, and a bearing cap. One half bearing held by the cylinder block includes: a first circumferential oil groove and a second circumferential oil groove being formed at positions opposite to an inlet of an oil passage of the journal part; a separation part separating the first circumferential oil groove and the second circumferential oil groove; and an oil hole penetrating from the first circumferential oil groove to an outer circumferential surface. A length L1 in a circumferential direction of the separation part at a position in the inner circumferential surface of the one half bearing is smaller than a length L2 in the circumferential direction of the inlet of the journal part.