The present invention provides a cover member for an internal combustion engine capable of improving the rigidity of a lid member of an internal combustion engine to suppress vibration and capable of smoothly guiding the oil flowing along the cover member to a through hole for supporting the shaft. A cover member (15) mounted on a crankcase (12) of an internal combustion engine (E) has a through hole (15d) rotatably supported by a shaft (11); a bulging portion (15f) which is located above the through hole and bulges toward the inside of the cover member; and a plurality of groove portions (15g) extending radially from the through hole so as to connect the upper portion and the lower portion on the inner surface side of the bulging portion. Therefore, it is possible to suppress the vibration by improving the rigidity of the cover member by the groove portion (15g) of the bulging portion (15f) without providing the ribs with weight, the oil inside the crankcase (12) can concentrated around the through hole (15d) along the groove portion (15g) of the bulging portion (15f) by means of the gravity, so that the rotating shaft can be efficiently lubricated.