A washing apparatus comprises: a washing tub for rotating on a rotating axis which is inclined toward a horizontal direction from a vertical direction or is set to be horizontal, and for receiving a washing article therein; a casing for covering the washing tub and for being filled with a cleaning liquid; a liquid supply flow path (3, 34) for supplying the cleaning liquid to the casing; a liquid discharge flow path (4, 41) for discharging the cleaning liquid from the casing; an air flow path that is formed vertically on the upper side of the casing and for opening an internal of the casing to an atmosphere; a detection portion for detecting, based on an amount of the cleaning liquid flowing into the air flow path, that an internal of the casing is filled with the cleaning liquid; and wherein, an air valve is provided to the air flow path that permits flow-in of air to the casing and discharge of air from the casing, and prohibits discharge of the cleaning liquid from the casing when the casing is full of the cleaning liquid; and wherein, when the air valve closes by the cleaning liquid flowing into the air flow path, the detection portion judges that the casing is filled with the cleaning liquid; a pump for sending out a cleaning liquid from the liquid discharge flow path (4, 41) to the liquid supply flow path (3, 34); wherein the apparatus is configured such that, in washing the washing article, after containing the washing article in the washing tub, the cleaning liquid is supplied to the casing by way of the liquid supply flow path (3, 34) in a condition that the casing is opened to an outside air by the air flow path; and the apparatus is configured such that, when the detection portion detects, based on an amount of the cleaning liquid flowing into the air flow path, that the casing is filled with the cleaning liquid, by permitting a circulation of the cleaning liquid from the liquid discharge flow path (4, 41), the cleaning liquid is circulated by the pump for the casing being filled with the cleaning liquid, and at a same time, the washing tub is rotated so as to start washing of the washing article. a washing tub for rotating on a rotating axis which is inclined toward a horizontal direction from a vertical direction or is set to be horizontal, and for receiving a washing article therein; a casing for covering the washing tub and for being filled with a cleaning liquid; a liquid supply flow path (3, 34) for supplying the cleaning liquid to the casing; a liquid discharge flow path (4, 41) for discharging the cleaning liquid from the casing; an air flow path that is formed vertically on the upper side of the casing and for opening an internal of the casing to an atmosphere; a detection portion for detecting, based on an amount of the cleaning liquid flowing into the air flow path, that an internal of the casing is filled with the cleaning liquid; and wherein, an air valve is provided to the air flow path that permits flow-in of air to the casing and discharge of air from the casing, and prohibits discharge of the cleaning liquid from the casing when the casing is full of the cleaning liquid; and wherein, when the air valve closes by the cleaning liquid flowing into the air flow path, the detection portion judges that the casing is filled with the cleaning liquid; a pump for sending out a cleaning liquid from the liquid discharge flow path (4, 41) to the liquid supply flow path (3, 34); wherein the apparatus is configured such that, in washing the washing article, after containing the washing article in the washing tub, the cleaning liquid is supplied to the casing by way of the liquid supply flow path (3, 34) in a condition that the casing is opened to an outside air by the air flow path; and the apparatus is configured such that, when the detection portion detects, based on an amount of the cleaning liquid flowing into the air flow path, that the casing is filled with the cleaning liquid, by permitting a circulation of the cleaning liquid from the liquid discharge flow path (4, 41), the cleaning liquid is circulated by the pump for the casing being filled with the cleaning liquid, and at a same time, the washing tub is rotated so as to start washing of the washing article.