A holder includes a first cover that covers a part of a corrugated tube in a radial direction of the corrugated tube, and a second cover engaged with the first cover and that covers a remaining part of the corrugated tube in the radial direction. A first retaining portion is formed on the first cover and is engaged in a groove on a bellows-shaped outer face of the corrugated tube. A second retaining portion is formed on the second cover and is engaged in the groove on the bellows-shaped outer face of the corrugated tube. The first cover includes a base portion and a pair of side wall portions extended vertically respectively from both ends of the base portion. The first retaining portion includes a first retaining piece which continuously extends from one of the side wall portions to the base portion and a second retaining piece which continuously extends from the other of the side wall portions to the base portion. The first retaining piece and the second retaining piece are separated from each other with air gap at the base portion.