A cubic boron nitride radius end mill includes a sintered cubic boron nitride compact bonded to an end of a main body, and a cutting edge provided on the sintered cubic boron nitride compact. The wedge angle θt of the cutting edge is constant over the entire region of the cutting edge. A negative rake face is disposed on a face so as to extend over the entire region of the cutting edge, and the rake angle θn of the negative rake face satisfies the relationship −30°≦θn≦−50°. A joint cutting edge is disposed between an end cutting edge and a radius cutting edge in the cutting edge, the joint cutting edge having a concave angle γ0 which is smaller than the concave angle γ1 of the end cutting edge and which satisfies the relationship 0.5°≦γ0≦2°.