To provide a cleaning agent for spray having sufficient cleaning power directly after spraying, and after spraying, having extremely little risk of metal erosion, such as the erosion of metal fins and others, and thereby needing no after-spray washing work.

An alkali component is added to a cleaning agent of neutral. The cleaning agent contains further a pH indicator. Due to the indicator, when the cleaning agent becomes neutral from alkalinity with evaporating alkali component, the color of the cleaning agent changes. The cleaning agent is sealed together with a propellant gas in an aerosol container, and the agent is sprayed from the container.