Disclosed is a drug solution injector comprising a needle tube having a sharp needlepoint at the distal end, a bottomed outer cylinder which is arranged on the base end side of the needle tube and has an inside space that can be communicated with the inside of the needle tube, a gasket slidable within the outer cylinder, a drug solution filled in the space formed by the outer cylinder and the gasket, a support member which supports the needle tube and has a flow channel having a distal end communicated with the inside of the needle tube and a base end communicated with the inside of the outer cylinder, an operation mechanism having a part covering at least the needlepoint of the needle tube, which mechanism performs selection between a communicated state wherein the inside of the needle tube and the inside of the outer cylinder are communicated with each other through the flow channel and a blocked state wherein the communication is blocked by rotating the support member, and an exposure prevention means for preventing exposure of the needlepoint.
