PURPOSE: To accurately adjust two rotor blades by connecting adjusting rings via a rotary wheel device having multiple pairs of planetary gears, and setting the sizes of a gear device so that the relative motion of the adjusting rings does not occur at the predetermined revolving speed ratio of fan rotors.

CONSTITUTION: A rotor blade 3a can be adjusted by an adjusting ring 16 connected to a first ball spindle 17, and a rotor blade 3b can be likewise adjusted by an adjusting ring 35 connected to a second ball spindle 36. The free end of the ball spindle 17 is connected to the gear 26a of a planetary wheel 25 via a planetary pin 20 as a gear device (adjusting ring) 19, and the free end of the ball spindle 36 is connected to one gear 26b of the planetary wheel 25. The planetary wheel 25 is fixed to a bridge 27. The sizes of the gears 26a, 26b are set so that the relative motion of the adjusting rings 19, 37 does not occur at the predetermined revolving speed ratio of fan rotors 7, 8, thus an adjustment can be accurately made.