An oil leakage detector of the present invention includes an image processing unit wherein the image processing unit calculates the values of saturation and intensity of each pixel in the color image of the object after an ultra-violet light is irradiated thereon, draws an intensity-saturation characteristic line of the saturation expressed in an X-axis and the intensity expressed in a Y-axis, sets an upper limit and a lower limit of intensity of each saturation as a threshold value based on an area without oil adhesion on the surface of the object, and determines, in the intensity-saturation characteristic line, an area corresponding to a pixel group where the intensity exceeds the threshold value of the upper limit and a pixel group where the intensity falls below the threshold value of the lower limit, to be an oil leakage adhered area.