To provide a work unit for erecting a pile which improves the workability by reducing the frequency of work for replacing a buffering member mounted on a cap body.

The work unit S is provided with an arm 90 and a boom 91. An attachment M1 for erecting the pile is mounted on a front part of the arm 90. The attachment M1 for erecting the pile comprises a mounting metal piece 1, a vibration generating device 2 for generating vibrations, and a cap body 3 for capping an upper part side of the pile. The cap body 3 is formed into a shape of a round tube and is mounted on a lower surface of a lower face plate 21 of the vibration generating device 2, in a manner of extending downward. Two rows of spacers 30 are fixed to the lower face plate 21, constituting an inside of the cap body 3, in parallel. A round rod-like engaging body 31 is fixed to an inner peripheral surface of the cap body 3. The cap body 3 is provided with liquid conveying pipes 32, 33 so that cooling water is sent to the inside from the outside through a peripheral wall part.