PURPOSE: To easily adjust a spreader by supporting the spreader on a control arm fixed on a mast so as to turn freely and turning this spreader by the opera tion of a cable through an adjusting means in a system for adjusting spreader of a shroud of a sailing boat.

CONSTITUTION: In an adjustable spreader arm system 10 consisting of two spreader arms 11 attached to a mast 1 of a sailing boat so as to move pivotally and freely, a horizontal rudder (yoke) 13 is provided across a predetermined distance from a top end of the mast 1, and a control arm 12 extending substantially in the vertical direction for the direction of movement of the sailing boat is fixed on this horizontal rudder 13. The spreader arm 11 is attached to this control arm 12 so as to turn freely around pivot pins 15 group. The spreader arm 11 is turned by an adjusting means including a halliard 16, and the halliard 16 is connected with ends of two cables 17 extending on a system 10 side through a block 18 and a pulley system 19.