To provide a linking mechanism almost generating no vibration nor noises, small in a friction loss high in machine efficiency, capable of being constituted to be compact and lightweight, and, used for a reciprocating piston compressor, a reciprocating piston pump, a press machine or the like.

The operations of at least a pair of pistons 11 and 11a moved in opposite directions in correlation with each other are converted into swinging rotational motions via a swing arm 15 having left and right parts equal to each other in mass and swinging rotational radius, then the motions are uniformly divided into two parts by connecting rods 43 and 43a and transmitted to a linking mechanism, and these are converted into the rotation of a rotary shaft 49 incorporated in the linking mechanism and then outputted.