To make it possible to simply mount a bucket with simple construction.

A first through-hole 24 of an arm 5 is fitted to a first pin hole 21 of a bucket 7 by interlocking a recess section of a hook mounted to the arm 5 with a boss section 23 of the bucket 7. By the constitution, the first pin hole 21 and first through-hole 24 are positioned to each other with simple operation interlocking the recess section with the boss section by moving the arm 5 so as to insert a first pin 9 to make it possible to simply connect the arm 5 to the bucket 7.