At present, some cooking appliances adopt a flip structure, as shown in FIG. 1, an upper cover 2′ of a cooking appliance is articulated with a base 1′, water vapor is generated when the product heats food 3′, part of the water vapor is condensed in the upper cover 2′, some food residue or soup may splash onto the upper cover 2′ in the heating process and flow down together with the condensed water when the cover is opened, a back plate on the back of the base 1′ is provided with a water retaining slope 11′ in most products in order to prevent the condensed water from directly dropping to contaminate a table or other furniture, the condensed water mixed with the food residue or soup may flow onto the water retaining slope 11′ between the upper cover 2′ and the base 1′ after the upper cover 2′ is opened, in this case, the problem that the condensed water drops to contaminate the furniture can be solved, but the condensed water mixed with the food residue or soup is gathered at the bottom position of the water retaining slope 11′, this position between the upper cover 2′ and the base 1′ is unlikely to clean, and if the food residue or soup is not cleaned, bacteria and peculiar smell are produced after a period of time, so that serious sanitation problem is caused to influence the use of the product.