PURPOSE: To enable the transfer of a seedling box at a high speed without causing the shift of the soil in the box by specifying the transfer speed of a piston rod having a chuck at the tip end.

CONSTITUTION: A chuck for holding or releasing a seedling box 1 is attached to the tip end of a piston rod 19 of a pneumatic cylinder 18. The chuck is constructed of a claw 27, a cylinder 28 and a rod. In the case of clamping a seedling box containing bed soil with the chuck and transferring the piston rod in the cylinder, the speed of the piston rod is lowered near the final stop position and the piston is laterally transferred at a high speed before the slow- down stage.