a working apparatus has : a working equipment for doing works on a structure ; a folding / unfolding mechanism for conveying the working equipment to the working position in a folded state ; a conveyance mechanism for conveying the working equipment and the folding / unfolding mechanism to the working position ; a pressing mechanism for pressing the working equipment against the lower surface of the structure ; and a traveling mechanism including a wheel for traveling along the lower surface of the structure and positioning the apparatus .