PURPOSE: To discriminate spoiled kerosene simply by passing the kerosene through a substance containing one or more kinds of specified material such as aluminum oxide and silicon oxide.

CONSTITUTION: Kerosene is passed through a substance containing at least one or more kinds of aluminum oxide, silicon oxide, magnesium oxide, calcium oxide and calcium chloride. As a result, spoiled components in the kerosene is absorbed away by the substance, which is colored according to the degree of the spoilage. This indicates the degree of the spoilage in the kerosene. For example, a glass tube 2 given a scale is filled with a filler 3 composed of an activated alumina of 60W80 mesh and then, the kerosene is poured through the opening 6 of the column. With the passage thereof, several colored layers are yielded.