An adhered-substance detecting apparatus for detecting an adhered substance appearing in a captured image photographed by an imaging apparatus installed at a vehicle, the adhered-substance detecting apparatus comprising: an outline extraction unit configured to extract an area of an outline of the adhered substance from the captured image as an outline area, wherein the outline area is at least one of: an edge area including an outline having an edge intensity within a specific range, a blur edge area whose luminance dispersion or frequency is within a specified range, an area including an outline having a peculiar shape wherein a processing for extracting that peculiar shape is applied to the captured image, a gradation area and an area whose luminance always changes darker or brighter after a movement of the vehicle; an inside extraction unit configured to extract an area inside the outline of the adhered substance from the captured image as an inside area, wherein the inside area is at least one of: an area with weaker edge intensity than the outline area, an area with low luminance under natural light, an area with high luminance at night, an area having grayish colors, an area having a pattern shape matching with a predetermined pattern shape, an area having a peculiar shape wherein a processing for extracting that peculiar shape is applied to the captured image, an area with low luminance dispersion and low frequency and an area whose luminance always changes to a certain value or only by a certain amount after a movement of the vehicle; an adhered-substance-detected area judgment unit configured to, when both the outline area and the inside area are extracted, compare the outline area with a predetermined shape or luminance of an outline of the adhered substance and detect the outline area with either one of matching shape and matching luminance as an adhered substance outline area, compare the inside area with a predetermined shape or luminance of an area inside an outline of the adhered substance and detect the inside area with either one of matching shape and matching luminance as an adhered substance inside area, and detect an area of the adhered substance, which is composed by overlaying the adhered substance outline area and the adhered substance inside area to one another to extract an adhered-substance-detected area. an outline extraction unit configured to extract an area of an outline of the adhered substance from the captured image as an outline area, wherein the outline area is at least one of: an edge area including an outline having an edge intensity within a specific range, a blur edge area whose luminance dispersion or frequency is within a specified range, an area including an outline having a peculiar shape wherein a processing for extracting that peculiar shape is applied to the captured image, a gradation area and an area whose luminance always changes darker or brighter after a movement of the vehicle; an inside extraction unit configured to extract an area inside the outline of the adhered substance from the captured image as an inside area, wherein the inside area is at least one of: an area with weaker edge intensity than the outline area, an area with low luminance under natural light, an area with high luminance at night, an area having grayish colors, an area having a pattern shape matching with a predetermined pattern shape, an area having a peculiar shape wherein a processing for extracting that peculiar shape is applied to the captured image, an area with low luminance dispersion and low frequency and an area whose luminance always changes to a certain value or only by a certain amount after a movement of the vehicle; an adhered-substance-detected area judgment unit configured to, when both the outline area and the inside area are extracted, compare the outline area with a predetermined shape or luminance of an outline of the adhered substance and detect the outline area with either one of matching shape and matching luminance as an adhered substance outline area, compare the inside area with a predetermined shape or luminance of an area inside an outline of the adhered substance and detect the inside area with either one of matching shape and matching luminance as an adhered substance inside area, and detect an area of the adhered substance, which is composed by overlaying the adhered substance outline area and the adhered substance inside area to one another to extract an adhered-substance-detected area. compare the outline area with a predetermined shape or luminance of an outline of the adhered substance and detect the outline area with either one of matching shape and matching luminance as an adhered substance outline area, compare the inside area with a predetermined shape or luminance of an area inside an outline of the adhered substance and detect the inside area with either one of matching shape and matching luminance as an adhered substance inside area, and detect an area of the adhered substance, which is composed by overlaying the adhered substance outline area and the adhered substance inside area to one another to extract an adhered-substance-detected area.