A landing gear includes a pair of skids, a cross tube and a stiffening portion. The pair of skids is arranged in parallel with a front-rear axis of an airframe of a rotary wing aircraft. The cross tube is attached to the airframe and coupling the pair of skids to each other. The cross tube includes curved portions located closer to end portions of the cross tube than to portions of the cross tube attached to the airframe. The stiffening portion suppresses flattening of the cross tube and is arranged in at least one of internal spaces of the curved portions or a stiffened portion located between a pair of curved portions. The stiffening portion includes an enlarged diameter portion which increases in diameter by an axial fastening power acting in an axial direction of the cross tube, and a fastening portion configured to generate the axial fastening power.