A washing machine includes a wash tub in which wash water is stored, a detergent supply device to supply detergent into the wash tub, and a water supply hose to supply the wash water from an external water supply source to the detergent supply device and subsequently into the wash tub. The contact insulating film includes at least one first recess and one second recess. As each brake unit is a small lump, the brake units can be easily made of material with high abrasion resistance, high temperature resistance, and low heat conduction, and the brake units still can sustain sufficient strength.