To provide a seedling box conveying device capable of adjusting an inclination of a seedling box feed base in response to difference of height between a road where a truck is stopped and a paddy field and exactly also exhibiting dropping off function of an empty box regardless of the inclination condition of the seedling box feed base.

A mounting part 8 capable of detachably mounting relative to a seedling conveying container 7 placed on a load-carrying platform 6A of the truck is provided at a base part side of the seedling box feed base of lengthy shape and an angle adjustment mechanism 10 for adjusting a mounting angle of the seedling box feed base 5 relative to the seedling conveying container 7 is provided at the mounting part 8. A seedling taking base part 9 for stopping/supporting a seedling growth box 2 is provided at a tip end of the seedling box feed base 5 and is provided fallably relative to the seedling box feed base 5. A horizontal retaining means 12 for retaining the seedling taking base part 9 to the approximately horizontal state is provided. A support part 90 for supporting the seedling growth box 2 is inclinably provided on the seedling taking base part 9. The support part 90 is constituted such that an end at the seedling box feed base 5 side is inclined relative to the seedling taking base part 9 by operation of an operation part 13 so as to be descended and the supported seedling growth box 2 can be dropped off to the inclined downward direction of the direction of the seedling box feed base 5.