PURPOSE: To improve counterweight installation work by fitting a base body part with an opening part to pass a hooking part through for hanging, and installing opposing-side-wall-parts, on the end part of the base body detachably in a downward astride state.

CONSTITUTION: A vibration type pile driver 1 is formed out of a hanger 4 which has a U-shaped cross section and is fitted with the hooking part 3 of a hook 2, and a vibrator 7 which is surrounded with a reaction weight 6 connected to the hanger 4 by a buffer coupling body 5, and a chuck 10 which is connected to the tip part of the piston rod 9 of the vibrator 7. A counterweight 20 is formed out of a rectangular-plate-shaped base body part 21 which has the opening part 25 of the hooking part 3 and a bolting hole, and a pair of opposing side wall parts 22, 23 projected down from the end part of the base body part 21. The counterweight 20 is installed on the pile driver 1 by lying the pile driver 1 and shifting the counterweight 20 horizontally.