To provide a blade device for allowing efficient blade work by enabling the turn of a blade around vertical and horizontal axes.

A mounted body 5 mounted on a boom 3 while supporting a blade 2 to be angle-changeable around the vertical axis comprises: a body part 11; boom side pivotal parts 12 provided on both right and left sides of the body part; a cylinder side connection part 13 provided on the horizontal center back side of the body part in an upward protruded shape higher than each of the right and left boom side pivotal parts; and a blade supporting part 14 provided on the horizontal center front side of the body part in a protruded shape, and supporting a mounting part 2A of the blade to be angle-changeable around the vertical axis. The blade supporting part 14 has angle setting means 16 between the mounting part 2A and itself for setting the angle of the blade 2 around the vertical axis, and the body part 11 has a reinforcing member 17 connecting the cylinder side connection part 13 to the right and left boom side pivotal parts 12, and sloping downward from the cylinder side connection part 13 to the boom side pivotal parts 12.