To provide a medical purpose hand piece in which an operating person can view the leading edge of a cutting tool and an operation can be performed at an angle at which cutting is easy.

The cutting tool 1, in which a cutting working section 1a for cutting an affected part is mounted at the leading edge of a flexible shank 1e, a casing 3 formed in a tubular form so that the cutting tool can be inserted, a medium member 4 mounted between both members so that the shank of the cutting tool may not be contacted with the inside of the casing, and a hand piece main portion 5 for removably holding the end portion of the cutting tool and conveying power from a motor to the cutting tool are included, the casing, the medium member, and the cutting tool are formed so that incurvating is possible within a predetermined range, and when curvature is made in this manner, plastic deformation of the casing is carried out, elastic transformation of the shank of the cutting tool is carried out, and the medium member is formed so as to follow the form variation of both the members.