PURPOSE: To facilitate attachment/detachment of a boom by tightening a rope end loop to fix a wishbone boom head to a mast by a tightening lever.

CONSTITUTION: A wishbone boom head 1 is provided with a curved pipe 2 of aluminum to which both beams 3 of the wishbone boom are inserted. The beams 3 are held on the curved pipe 2 by snap lock members 4. A connection member is integrally formed with the curved pipe 2, and this connection member can be engaged with a mast 5 of a surfboard, and it comprises a sleeve-like collar 6 to be fixed and connected to the mast 5, a circumferential wall part 7 to contain the curved pipe 2, and two webs radially provided to the collar 6. A lock flap 10 bent to correspond to the mast 5 is integrally injection-moulded through a film hinge 11. For fixing the head 1 to the mast 5, a loop 14 at a rope end 13 is hooked on a groove in a protrusion 20, so it can be operated by a lever 12.