To provide an iron tapping hole boring machine which can obviate the necessary setting number, by providing new function to the conventional type.

The boring machine is composed of a supporting column 4 fixed on a casting floor interposed between adjacent two iron tapping runners 28, 28, a main boom 6 supported so as to be swingable with a swing supporting part 22 coaxially fitted to the supporting column at the one end and providing a rotary supporting part 7 at the outer end and loading a rotary driving device 16 for driving this rotary supporting part and having the length passable just above two iron tapping runners in the swing locus of the other end, an auxiliary boom 8 supported so as to be turnable around the rotary supporting part with the rotary supporting part and a guide channel 11 connected with the auxiliary boom so as to be inclinable with an inclining link and loading a drill hammer fitting a boring rod so as to be possible to advance/retreat.