An internal combustion engine includes an oil seal mounted at a crankshaft of an internal combustion engine body to restrain leakage of oil to an outside of the internal combustion engine, an oil seal fixing member fixed to the internal combustion engine body to fix the oil seal to the internal combustion engine body, and a cover member assembled on a lateral surface portion of the internal combustion engine body in a direction in which the crankshaft extends, the cover member covering the oil seal fixing member from a side opposite to the internal combustion engine body, the oil seal fixing member being fixed to the internal combustion engine body at a fixing position which is provided at an inner side than an outer edge portion of the cover member fastened to the internal combustion engine body.