To provide a mechanism converting reciprocation into rotating movement, and rotating movement into reciprocation as a mechanism of a method improved in converting efficiency better than a conventional method in regard to mechanical apparatuses using kinetic energy.

The structure is provided wherein an inner side of a reciprocating mass 1 is formed as an endless shape, a rotor 2 is contacted to it, and energy conversion is continuously carried out. A contact part of the reciprocating mass 1 and the rotor 2 is structured to not cause slipping (e.g. gears or the like). An auxiliary mechanism is prepared to carry out guiding such that the reciprocating mass 1 can reciprocate on a certain track.