A dental handpiece having a reciprocal rotation means for converting a rotary motion to a reciprocating rotating motion is disclosed. The reciprocal rotation means includes a rotary body having input- and output-side guide grooves, input- and output-side semispherical concave surface formed at the ends of input- and output-side shaft part, respectively, of a rotary shaft extending in a grip of the handpiece, and input- and output-side guide pin protruding from the input- and output-side semispherical concave surface, respectively for engagement in the input- and output-side guide grooves, respectively.