PURPOSE: To control rotational moving angle of a bucket constant by connecting a boom, an arm, and a bucket with two connecting pins, and in parallel with the connected line, providing a link for the arm which is able to rotationally move the bucket and the arm freely.

CONSTITUTION: The front construction member of a main body 1 is constituted so that a boom 2 and an arm 4 are connected through a first connecting pin 3, and an arm 4 and a bucket 6 are connected through a second connecting pin 5, and respectively provided with driving devices 7, 8. The extreme end part of the boom is instituted to have a large width size, and the one end is rotationally movably connected to the bucket 6 through a third connecting pin 20. Further, a link 21 for the arm is provided in parallel with the direction connecting the first connecting pin 3 and the second connecting pin 5, and the one end is rotationally movably connected to the boom 2 through a fourth connecting pin 22. Hereby, the rotational moving angle of the bucket 6 can be controlled so as to be a constant angle.