A needle assembly for injecting a drug intradermally, the needle assembly comprising: a needle tube having a needle tip; a needle hub that holds the needle tube; a needle protection member displaceable along an axial direction of the needle tube; a rotor provided at a proximal end of the needle protection member; and an urging member provided on the needle hub to urge the rotor and the needle protection member toward a distal direction of the needle tube, wherein the needle protection member is located at a use position at which the needle tip is exposed when displaced in a proximal direction of the needle tube from a protection position at which the needle tip is covered, wherein the rotor includes a rotor body, and a restriction portion provided on the rotor body, wherein the restriction portion is displaced from an initial position to a lock position by the rotor body rotating with respect to the needle protection member when the needle protection member in an initial state is displaced from the protection position to the use position and returns to the protection position, and wherein the needle hub is provided with a displacement prevention portion that prevents the needle protection member from being re-displaced from the protection position to the use position by contacting the restriction portion at the lock position, characterized in that the needle protection member is provided on the needle hub, and in that the needle assembly further comprises: a rotation restriction portion that restricts a rotation of the needle protection member with respect to the needle hub along a circumferential direction of the needle tube. a needle tube having a needle tip; a needle hub that holds the needle tube; a needle protection member displaceable along an axial direction of the needle tube; a rotor provided at a proximal end of the needle protection member; and an urging member provided on the needle hub to urge the rotor and the needle protection member toward a distal direction of the needle tube, wherein the needle protection member is located at a use position at which the needle tip is exposed when displaced in a proximal direction of the needle tube from a protection position at which the needle tip is covered, wherein the rotor includes a rotor body, and a restriction portion provided on the rotor body, wherein the restriction portion is displaced from an initial position to a lock position by the rotor body rotating with respect to the needle protection member when the needle protection member in an initial state is displaced from the protection position to the use position and returns to the protection position, and wherein the needle hub is provided with a displacement prevention portion that prevents the needle protection member from being re-displaced from the protection position to the use position by contacting the restriction portion at the lock position, characterized in that the needle protection member is provided on the needle hub, and in that the needle assembly further comprises: a rotation restriction portion that restricts a rotation of the needle protection member with respect to the needle hub along a circumferential direction of the needle tube.