Abstract: A dust cover includes a bellows-like portion which is comprised of a large-pitched portion and a small-pitched portion in succession, each having a plurality of alternating ridges and grooves of uniform diameter. The ridges and grooves of the large-pitched portion are spaced at an equal but large pitch while the ridges and grooves of the small-pitched portion are spaced at an equal but smaller pitch. The ridges of the small-pitched portion have a thickness smaller than that of the ridges of the large-pitched portion. When a force is applied to the dust cover in a direction of contraction, the dust cover first contracts at the small-pitched portion and then at the large-pitched portion, whereby undesired buckling thereof is kept to a minimum. A method for blow molding the dust cover is also disclosed.