EXCAVATOR AND EXCAVATION METHOD

PROBLEM TO BE SOLVED: To provide an excavator capable of increasing the change amount of an excavation diameter without causing an increase in the size of a machine.SOLUTION: An excavator 10 for excavating a pile hole 1 with the rotation and revolution of a plurality of drum cutters 40 includes a main shaft 12 arranged along the revolution axis, a revolution part 20 rotatably supported by the main shaft 12, a revolution hydraulic motor 50 for rotating the revolution part 20, a plurality of arms 35 which is supported by the revolution part 20 so as to be turnable around their turn axes parallel to the revolution axis, which support the drum cutters 40 at their front end sides so that their rotation axes are inclined to a plane perpendicular to the revolution axis, and which is turned to move them forward and backward in the outer-diameter direction of the revolution axis, a rotation hydraulic motor 60 for rotating the drum cutters 40 around their rotation axes, and a diameter-adjustment hydraulic motor 33 for turning the arms 35 around their turn axes.