A vessel comprising: a vessel body; and a cover body, wherein the vessel body comprises: a vessel main body being tubular and having an upper open-end and a lower closed-end; and a cover body containing portion being cylindrical tubular and having at least one open-end, wherein the cover body containing portion is at the upper open-end of the vessel main body and the vessel main body and the cover body containing portion are arranged such that an axial direction of the vessel main body is approximately perpendicular to an axial direction of the cover body containing portion, wherein an inside of the vessel main body is in communication with an inside of the cover body containing portion through the upper open-end, wherein an opening portion is provided at a side wall of the cover body containing portion over the upper open-end of the vessel main body, wherein the cover body is cylindrical columnar and has a through-hole in a direction perpendicular to an axial direction of the column, and two sealing portions at positions opposed to each other in a radial direction of the cover body and shifted from an opening of the through-hole in a peripheral direction, wherein the cover body is coaxially and rotatably containable in an inside of the cover body containing portion in a condition where an outer peripheral surface of the cover body is in contact with an inner peripheral surface of the cover body containing portion, wherein the through-hole of the cover body is at a position corresponding to the side wall opening portion of the cover body containing portion and the upper open-end of the vessel main body in a condition where the cover body is contained in the cover body containing portion, wherein in a condition where the cover body is contained in the cover body containing portion, when the cover body is rotated and one end of the through-hole is placed below the side wall opening portion and the other end of the through-hole is placed above the upper open-end of the vessel main body, the inside of the vessel main body is communicated with the side wall opening portion through the through-hole, wherein, when the cover body is rotated and the sealing portion is placed over the upper open-end of the vessel main body, the inside of the vessel main body is sealed from the outside, characterized in that an inner diameter X of the cover body containing portion in a direction perpendicular to the axial direction of the cover body containing portion, and an outer diameter Y of the cover body in the radial direction at the two sealing portions, satisfy a relationship of Y > X, and wherein the vessel comprises a ribbed surface at an inner peripheral surface of the cover body containing portion adjacent to the upper open-end. a vessel body; and a cover body, wherein the vessel body comprises: a vessel main body being tubular and having an upper open-end and a lower closed-end; and a cover body containing portion being cylindrical tubular and having at least one open-end, a vessel main body being tubular and having an upper open-end and a lower closed-end; and a cover body containing portion being cylindrical tubular and having at least one open-end, wherein the cover body containing portion is at the upper open-end of the vessel main body and the vessel main body and the cover body containing portion are arranged such that an axial direction of the vessel main body is approximately perpendicular to an axial direction of the cover body containing portion, wherein an inside of the vessel main body is in communication with an inside of the cover body containing portion through the upper open-end, wherein an opening portion is provided at a side wall of the cover body containing portion over the upper open-end of the vessel main body, wherein the cover body is cylindrical columnar and has a through-hole in a direction perpendicular to an axial direction of the column, and two sealing portions at positions opposed to each other in a radial direction of the cover body and shifted from an opening of the through-hole in a peripheral direction, wherein the cover body is coaxially and rotatably containable in an inside of the cover body containing portion in a condition where an outer peripheral surface of the cover body is in contact with an inner peripheral surface of the cover body containing portion, wherein the through-hole of the cover body is at a position corresponding to the side wall opening portion of the cover body containing portion and the upper open-end of the vessel main body in a condition where the cover body is contained in the cover body containing portion, wherein in a condition where the cover body is contained in the cover body containing portion, when the cover body is rotated and one end of the through-hole is placed below the side wall opening portion and the other end of the through-hole is placed above the upper open-end of the vessel main body, the inside of the vessel main body is communicated with the side wall opening portion through the through-hole, wherein, when the cover body is rotated and the sealing portion is placed over the upper open-end of the vessel main body, the inside of the vessel main body is sealed from the outside, characterized in that an inner diameter X of the cover body containing portion in a direction perpendicular to the axial direction of the cover body containing portion, and an outer diameter Y of the cover body in the radial direction at the two sealing portions, satisfy a relationship of Y > X, and wherein the vessel comprises a ribbed surface at an inner peripheral surface of the cover body containing portion adjacent to the upper open-end.