Method of manufacturing dishwasher

A method of manufacturing a dishwasher having an inner wall made of a stainless steel plate, comprising steps of:

• forming a first layer comprising zirconium oxide and silicon oxide on a surface of the inner wall at a heat treatment temperature of 200° C. or higher;
• forming a second layer comprising an oxoacid on a surface of the first layer at a heat treatment temperature lower than the heat treatment temperature of the first layer;
• and
• obtaining a thin-film layer comprising zirconium oxide and silicon oxide on the surface of the inner wall and having a contact angle of water of 20 degrees or less on the surface, after removing the second layer by using a washing method,
• wherein the first layer contains the zirconium oxide in an amount of 80 mass % or more in terms of oxide and the silicon oxide in an amount of 1 mass % to 20 mass % in terms of oxide.