PURPOSE: To provide a fuel assembly using no extra portion for a rotation preventing means of short fuel rods, having a simple structure, and widening the application range without increasing the local pressure loss.

CONSTITUTION: Short fuel rods 11B are partially used among many fuel rods 11 arranged squarely. A screwed lower end plug 11e is fitted at the lower end and screwed into the pedestal 13a of a lower tie plate 13, a solid column-like upper end plug 11e is fitted at the upper end, and vertical coupling sections 17 such as grooves or slits are provided on both sides of the upper end plug 11d. A spacer spring 16 fitted to a block wall surrounding the unit cell 14c of a spacer 14 arranged at the height position of the coupling sections 17 is coupled with the vertical coupling sections 17.