PURPOSE: To absorb the lateral flexure due to the longitudinal torsion of a hatch cover edge material under sailing, by making wide the flange step width and the packing receiving material of a guide travel wheel of a foldable hatch cover.

CONSTITUTION: The width of a flange step of a gruide travel wheel 13 provided at the side of a panel 2 of hatch cover constructed such that a hatch panel having rotatable ends will be foldable is made wider than the width of rail top face of the guide rails 121, 122. The receiving material of a water-tight packings 191, 192 placed between the lower face of said hatch panel 2 and the horizontals 171, 172 of the edge materials 101, 102 is also made wide. Consequently the lateral flexure due to longitudinal torsion of a hatch cover edge material under sailing caused by wave and mounted load can be absorbed to maintain water- tightness thus to prevent intrusion of sea water through the hatch opening.