PURPOSE: To prevent progressive movement of rotors which results from the generation of not only tangential resilient distortion but also tangential stress due to inertia and gravity.

CONSTITUTION: This converting mechanism includes: a pair of opposite component elements 4, 5 permitting conversion of rotational movement into linear movement and vice versa, one of which elements is rotatable while the other of the elements is forced to move along a circular shaft which guides rolling surfaces; opposite rolling surfaces 7, 8 each having a corrugated outer form; rotors 14 rigidly inserted between the rolling surfaces 7, 8 in a regularly spaced apart relation to one another so as to rotate on the rolling surfaces without slip, the number of the rotors 14 corresponding at most to the number of corrugations on the rolling surfaces 7, 8; and a pressing device 26 capable of producing axial force on the second component element 5 to assure a mutual contact between the component elements 4, 5 and the rotors 14.