The invention relates to mechanical engineering, and more particularly to a curved groove ball bearing mechanism, in which a pair of curved groove ball bearings without a retainer are symmetrically arranged to enable the conversion between the rotary motion and the reciprocating linear motion. The bearing mechanism includes an inner ring, a first outer ring, a second outer ring, a plurality of first steel balls and a plurality of second steel balls. The invention is capable of achieving the conversion between the rotary motion of the inner ring into the reciprocating linear motion of the first and second outer rings.