To reduce noises to be generated by a collision between a bucket and a bucket bracket.

Seat boards 9 are welded at left - right two places on a plate 3 installed onto the top face of a pinching recessed section 43 formed to the upper section of the rear of a bucket 1, and holding pieces 5 in which bolts 4 are inserted to rears are mounted on the seat boards 9. Relating pieces 6, which have connecting sections 62 in which the bolts 4 are screwed and in which press-contacting sections 61 are formed to the lower sections of the connecting sections 62, are arranged at the rears of the holding pieces 5, and the press-contacting sections 61 are abutted against the retaining section 13 of a bucket bracket 2 and the bolts 4 are screwed to the connecting sections 62. The retaining pieces 6 have guide sections 63 pinching the seat boards 9 towards a front and guiding the movement of the retaining pieces 6, and are pulled to the front by the screwing of the bolts 4 and the bucket bracket 2 is brought into press-contact with the bucket 1.