PURPOSE: To insert an object in a rod condition into the tube of a tubular unit to be assembled and further to move the rod object automatically smoothly inserted relating to a horizontal hole of this tubular unit to be assembled.

CONSTITUTION: A device comprises a chuck 5 for chucking a rod 3 so as to insert it into a horizontal hole 2 of a tubular unit 1 to be assembled, first mover 11 for vertically moving the rod 3, second mover 14 for carrying this rod 3 from an assembling start point to the unit to be assembled, a rotary unit 6 for obliquely rotating the rod 3 along an upper end of the horizontal hole 2 of the unit to be assembled and a control unit 17 for respectively controlling these chuck, moves and rotary unit.