Abstract: The present invention provides an oil detecting element capable of accurately detecting oil floating on water. The oil detecting element comprises a water-repellent, oil-passing filtering member for preventing water coming into the element. Oil can be detected by detecting change in electric resistance of a conductive particle layer due to its contact with oil arriving through the member. According to an embodiment of the invention, the water-repellent, oil-passing filtering member is impregnated with a material which is toxic to water life such as algae and shells to prevent settling of these water life on the surface of the element and thereby to prolong the life of the element. Examples of an oil detector incorporating the oil detecting element and including an electrical circuit which detects change in electric resistance of the element upon its contact with oil and actuates a suitable alarming device such as a buzzer are described.