To provide a mechanical motion mechanism giving the resilient force of an energy storing spring in one direction and the other alternatively.

In this mechanical motion mechanism, a square link assembly is formed of first to fourth links 1 to 4, and the first link 1 is provided with a energy storing spring 5, which gives spring force to the first and fourth links 1 and 4 in the directions opposite to each other, and the second link 2 has first and second turning supporting points P1 and P2 respectively, and the fourth link 4 opposing to the second link 2 has third and fourth turning supporting points P2 and P4 respectively, and a pair of the first and third turning supporting points P1 and P3 and a pair of the second and fourth turning supporting points P2 and P4 are made free alternatively by a supporting point switching mechanism. The square link assembly is made to perform oblique deformation in one direction in which the second and fourth supporting points P2 and P4 become a center and in another direction in which the first and third turning supporting points P1 and P3 become a center alternatively by making the energy storing spring force of the energy storing spring 5 work to the end section of the second link 2 and the end section of the fourth link 4 alternatively.