To provide a method for arranging an under-block for securing safety of a worker, preventing damage to a machine and the under-block, and improving installation accuracy, while allowing easy rearrangement of the under-block.

The method for arranging an under-block includes: a block preparing process that installs the under-block 1 in a block storage area 28A in a range to be held by a spindle 30; a tool mounting process that mounts on the spindle a tool 10 for moving the under-block having a main shaft mounting part mounted on the spindle, a block holding part 14 for holding the under-block and a pivot mechanism 15 for turning the block holding part around a horizontal pivot shaft; and a block arrangement process that arranges the under-block at a work mounting position of a table 28 with the tool for moving the under-block by relative movement. The block arrangement process includes an action for changing the posture of the under-block while the under-block is held.