To perform an easy and high-precise work to set the reference value of a drill tip when the point protrusion direction of a boring head is obliquely set.

In a reference setting jig for a boring head, a reference value set part 3 set at the upper part of a jig body 2 comprises a holder 4; and a reference value setting member 5 mounted rotatably around a horizontal axis. A horizontal plane passing a horizontal rotation center line O-O and paralleling a horizontal rotation center line is formed as a reference surface 6 at a reference value set member 5 and a reference hole 7 into which the center pin of a drill tip is inserted is formed in the reference surface 6. Further, the holder 4 is rotatable around a vertical axis P-P passing through the reference hole 7 and crossing a horizontal rotation center line at right angles based on the jig body 2 and the reference surface 6 is three-dimensionally displaceable.