Method and device for boring non-round hole

A non-round hole boring device capable of machining a work in a desired cross sectional shape by a simple configuration. The non-round hole boring device (1) comprises cylindrical arbors (11, 21), shafts (12, 22) stored in the arbors (11, 21), respectively, a cutting tool (13) attached to the outer peripheral surface of the arbor (11), a cam (121) formed on the shaft (12) and pressing the cutting tool (13), a first rotary encoder (252), a second rotary encoder (241), an arbor motor (23) for rotatingly driving the arbors (11, 21), a shaft motor (24) for rotatingly driving the shafts (12, 22), and a controller (40). The controller (40) advances or retards the phases of the rotating angles of the shafts (12, 22) relative to the phases of the rotating angles of the arbors (11, 21), respectively, while rotating the arbors (11, 21) and the shafts (12, 22) in synchronism with each other, respectively. Consequently, the cutting tool (13) is pressed by the cam (121) to adjust the projecting dimension of the cutting tool (13).