An intake device for an internal combustion engine, the intake device comprising: - a housing constituting an intake passage; - a valve element including a valve portion arranged to be rotated around an axis, to open and close a part of the intake passage, and thereby to strengthen an intake air flow; and - a receiving portion which is formed on a bottom wall of a housing passage of the housing, and which is recessed in an arc shape along a movement trajectory of the valve portion, wherein: - the valve portion includes an outer side surface which confronts a bottom surface of the receiving portion at a valve opening position, the outer side surface having an arc shape, and the outer side surface including a seal portion that has a raised shape, and that extends along an edge portion of the outer side surface on an upstream side of an intake direction at the valve opening position, and second seal portions each of which having a raised shape, and which are provided along another edge portion of the outer side surface on a downstream side of the intake direction at the valve opening position, only on both sides of an aeration window of the valve portion formed at a center of the other edge portion on the downstream side of the intake direction at the valve opening position, - the valve element includes a pair of side wall portions positioned at both ends of the valve portion in an axial direction; - a side seal portion (64, 66) is provided on an outer side surface of each of the pair of the side wall portions confronting side wall surfaces of the intake passage; - each of the side seal portions (64, 66) has a raised shape; - each of the side seal portions (64, 66) is continuous with the respective seal portion (60, 62); - each of the seal portion, the second seal portion, and the side seal portions (64, 66) has a rectangular section; - each of the seal portion and the second seal portion includes a tip end portion confronting the bottom surface with a minute clearance therebetween at the valve opening position; and - each of the side seal portions (64, 66) includes a tip end portion confronting the side wall surfaces of the intake passage with a minute clearance therebetween. - a housing constituting an intake passage; - a valve element including a valve portion arranged to be rotated around an axis, to open and close a part of the intake passage, and thereby to strengthen an intake air flow; and - a receiving portion which is formed on a bottom wall of a housing passage of the housing, and which is recessed in an arc shape along a movement trajectory of the valve portion, - the valve portion includes an outer side surface which confronts a bottom surface of the receiving portion at a valve opening position, the outer side surface having an arc shape, and the outer side surface including a seal portion that has a raised shape, and that extends along an edge portion of the outer side surface on an upstream side of an intake direction at the valve opening position, and second seal portions each of which having a raised shape, and which are provided along another edge portion of the outer side surface on a downstream side of the intake direction at the valve opening position, only on both sides of an aeration window of the valve portion formed at a center of the other edge portion on the downstream side of the intake direction at the valve opening position, - the valve element includes a pair of side wall portions positioned at both ends of the valve portion in an axial direction; - a side seal portion (64, 66) is provided on an outer side surface of each of the pair of the side wall portions confronting side wall surfaces of the intake passage; - each of the side seal portions (64, 66) has a raised shape; - each of the side seal portions (64, 66) is continuous with the respective seal portion (60, 62); - each of the seal portion, the second seal portion, and the side seal portions (64, 66) has a rectangular section; - each of the seal portion and the second seal portion includes a tip end portion confronting the bottom surface with a minute clearance therebetween at the valve opening position; and - each of the side seal portions (64, 66) includes a tip end portion confronting the side wall surfaces of the intake passage with a minute clearance therebetween.