A chain case disposed opposite an interval between a cylinder block and a cylinder head sandwiching a gasket includes a liquid sealing material guiding recessed portion that opposes the interval and is entirely surrounded by a seal surface. During seal structure formation, a large amount of a liquid sealing material is caused to flow forcefully toward the interior of the interval when an operation is performed to fasten the chain case to the cylinder block and the cylinder head such that the liquid sealing material flows to the innermost portion of the interval, and as a result, the liquid sealing material can reach an end portion of the gasket reliably. Hence, the liquid sealing material can flow sufficiently to positions requiring sealing, whereby lubricating oil leakage from the interior of the chain case can be prevented.