A printed image inspecting apparatus for reading out printed images on a printing sheet, which have been printed on said printing sheet in accordance with printed image data, the printed image data including front printed image data for printing one printed image of said printed images on a front face of the printing sheet and back printed image data for printing another printed image of said printed images on a back face of the printing sheet, and for inspecting a printing result of the printing sheet, the printed image inspecting apparatus comprising: a reader (17, 25) configured to read said front and back faces of the printing sheet, on both faces of which said printed images have been printed in accordance with the printed image data, to obtain front inspecting image data and back inspecting image data, respectively, the front inspecting image data being obtained from the printed image printed on the front face of the printing sheet in accordance with the front printed image data, and the back inspecting image data being obtained from the printed image printed on the back face of the printing sheet in accordance with the back printed image data; a mask generating unit configured to generate a show-through area mask, representing an area where show-through possibly exists by aligning inverted front printed image data of the printed image data with the back printed image data of the printed image data and removing an image of the back printed image data, the inverted front printed image data being obtained by inverting the front printed image data in a horizontal direction; and a determining unit configured to inspect a show-through area of the back inspecting image data corresponding to the show-through area mask with a show-through inspection threshold and to inspect an area other than the show-through area with a normal inspection threshold having a stricter value than the show-through inspection threshold. a reader (17, 25) configured to read said front and back faces of the printing sheet, on both faces of which said printed images have been printed in accordance with the printed image data, to obtain front inspecting image data and back inspecting image data, respectively, the front inspecting image data being obtained from the printed image printed on the front face of the printing sheet in accordance with the front printed image data, and the back inspecting image data being obtained from the printed image printed on the back face of the printing sheet in accordance with the back printed image data; a mask generating unit configured to generate a show-through area mask, representing an area where show-through possibly exists by aligning inverted front printed image data of the printed image data with the back printed image data of the printed image data and removing an image of the back printed image data, the inverted front printed image data being obtained by inverting the front printed image data in a horizontal direction; and a determining unit configured to inspect a show-through area of the back inspecting image data corresponding to the show-through area mask with a show-through inspection threshold and to inspect an area other than the show-through area with a normal inspection threshold having a stricter value than the show-through inspection threshold.