To provide a jib crane hatch collision-preventing method in an unloader for grain, which can automate collision avoidance.

This unloader for grain is provided with an elevator part 17 at the tip of a main boom 3 projected on a hatch of a ship brought alongside the pier by a main swivel tower on a quay, and with a jib crane 2 capable of swiveling on the main swivel tower 4. At least in swiveling the main boom 3, the position of the hatch 18 measured by a sensor fitted to the jib crane 2 is previously stored, the current position by the movement of a hook 14 due to swivel of the main boom 3 is computed, and the swivel of the main boom 3 is regulated by checking the current position of the hook 14 with the position of hatch 18 so that the hook 14 does not collide with the hatch 18.