A liquid administration device comprising: a cylindrically-shaped cylindrical body configured to be filled with liquid in its inside; a needle tube configured to be provided being communicated or communicable with the cylindrical body at a tip side of the cylindrical body, and to have a sharp needle tip at a tip; a gasket configured to be capable of sliding within the cylindrical body; an operation member configured to perform pressing operation to discharge the liquid from the needle tube by pressing the gasket toward a tip direction; a restricting member configured to be arranged at an outer peripheral side of the cylindrical body, and to be capable of restricting the pressing operation; and a cover member configured to be capable of moving to a first position, in which at least the needle tip of the needle tube is covered, and to a second position, retreated to a base end direction from the first position, in which the needle tip is exposed, characterized in that a slider part is provided to one member out of the operation member and the restricting member, and a rail part, in which the slider part slides, is provided to the other member, the rail part having a longitudinal direction rail formed in the same direction as an operation direction during the pressing operation, and a lateral direction rail continued to the longitudinal direction rail and formed in the direction perpendicular to the operation direction; when the cover member is in the first position, the slider part is positioned in the lateral direction rail and makes the pressing operation impossible, and when the cover member moves from the first position to the second position, the slider part moves from the lateral direction rail to the longitudinal direction rail in conjunction with the movement, thereby the pressing operation is made possible. a cylindrically-shaped cylindrical body configured to be filled with liquid in its inside; a needle tube configured to be provided being communicated or communicable with the cylindrical body at a tip side of the cylindrical body, and to have a sharp needle tip at a tip; a gasket configured to be capable of sliding within the cylindrical body; an operation member configured to perform pressing operation to discharge the liquid from the needle tube by pressing the gasket toward a tip direction; a restricting member configured to be arranged at an outer peripheral side of the cylindrical body, and to be capable of restricting the pressing operation; and a cover member configured to be capable of moving to a first position, in which at least the needle tip of the needle tube is covered, and to a second position, retreated to a base end direction from the first position, in which the needle tip is exposed, characterized in that a slider part is provided to one member out of the operation member and the restricting member, and a rail part, in which the slider part slides, is provided to the other member, the rail part having a longitudinal direction rail formed in the same direction as an operation direction during the pressing operation, and a lateral direction rail continued to the longitudinal direction rail and formed in the direction perpendicular to the operation direction; when the cover member is in the first position, the slider part is positioned in the lateral direction rail and makes the pressing operation impossible, and when the cover member moves from the first position to the second position, the slider part moves from the lateral direction rail to the longitudinal direction rail in conjunction with the movement, thereby the pressing operation is made possible.