PURPOSE: To provide a guide device for a large main sail winding pipe arranged in parallel with the mast of a sailing boat, connected to a driving mechanism and a lower sail beam for respectively expanding and winding the large main sail and adjacent to and held by the mast through at least one horseshoe member.

CONSTITUTION: A guide device for a large main sail winding pipe includes at least one cable or a rod 26. The cable or the rod 26 is fixed to the fitting 28 of the top part of a mast and a lower sail beam 6 so as to extend in parallel with a winding pipe 3. The cable or the rod 26 is held in its stretched state and connected to parts near the ends of horseshoe members 13 and 13a. The horseshoe members themselves are connected to the mast 1 by pivotally attaching mechanisms.