The invention relates to a cleaning structure, an indoor unit of an air conditioner and the air conditioner. The cleaning structure is applied to the air conditioner, and comprises a water storage portion and a water spraying portion. The water storage portion comprises a holding cavity. A water filling opening and a water outlet are formed in the holding cavity. The water filling opening communicates with an external water source through a pipeline. The water spraying portion communicates with the water outlet and is set to spray water to an air channel of the air conditioner. Due to the factthat the cleaning structure with the water spraying function is arranged in the air channel of the air conditioner, removal of dust and dirt in the air channel of the air conditioner is achieved; andthe cleaning structure further has a certain water storage capacity, the cleaning structure still can work under the condition that water supply of the external water source is insufficient, the structure is simple, and the operation is convenient.