Internal combustion engine and structure of chain cover of the same

An internal combustion engine (100, 500, 600, 700, 800) includes: a chain cover (20, 320, 420, 520, 620, 720, 820) that is attached to an internal combustion engine main body (10) having a crankshaft (40); an oil seal (5) that is mounted on the crankshaft in the vicinity of the chain cover; a metallic oil seal fixing member that is disposed on a surface of the chain cover and fixes the oil seal, the surface being present opposite to the internal combustion engine main body; and a first sealing member (6) that is disposed between the oil sealing fixing member and the chain cover.