To suggest a durable drill used for a resin insulating substrate containing hydroxide particles.

A stress applied by cutting chips is reduced by setting an angle of torsion to 42 to 53°, making the drill less breakable. Further, a roughness Ra of a surface of a cutting chips discharge groove is set to 0.01-0.11 μm. When the roughness Ra is less than 0.01, the drill may be broken, resulting from a flaw. On the other hand, when the roughness Ra is beyond 0.11, a discharge of the cutting chips is blocked and the drill is broken more easily by the stress applied by the cutting chips.