A liquid administration device includes an inner structure that includes a cylindrical body that has a bottom part in a distal portion thereof and an opening portion in a proximal portion thereof, a needle tube that is mounted in the distal portion of the cylindrical body and has a sharp needle tip at a distal end and a proximal end of which is communicatable with an inside of the cylindrical body, and a gasket that is located in the cylindrical body an operation member that includes a plunger, the operation member being configured to perform a pressing operation in which the plunger is moved relative to the cylindrical body in a distal direction while being pressed an engagement portion that includes: a first engagement portion and a second engagement portion.
