To provide a device and a method of machining a bore capable of preventing a high stress from being generated around the bore positioned between the bores to be machined and parallelism of a workpiece from being deteriorated, and suppressing the shape deformation of the bore positioned between the bores to be machined when machining every other bore.

In the bore machining device 10, a second machining tip 33 is disposed at a second shaft head 23 so as not to be the same phase with respect to a first machining tip 31, and so as not to be the opposing phase with respect to the first machining tip 31 by rotating by 180°. Specifically, the second tip 33 is disposed at the second shaft head 23 so as to be the phase rotated by 45° in the rotational direction of the second shaft head 23 with respect to the first machining tip 31 in a planar view.