PURPOSE: To provide a light-weight, highly reliable gyrocraft rotor hub body wherein only centrifugal force of a blade operates as a load, and in addition, to provide the rotor hub body suitable for manufacturing with composite materials.

CONSTITUTION: This gyrocraft rotor hub body 1 has a form wherein each blade is connected with the rotor hub body 1 by joint-connecting members. The gyrocraft rotor hub body 1 consists of two rings 7, 8 located in the plane, which cross at right angles with an axle line extending from a column to a rotor in parallel with each other. These two rings 7, 8 are provided across a thin wall having an opening part 10 which is larger enough to insert the joint in. Supporting points for fixing the joint are fixed by a fixing member supported by holes 12, 14 of the rings 7, 8. As a result, a hard brace is formed, which enables power transmission.