PURPOSE: To reduce shock force generation mechanism to put on a moving object and minimize and lighten the device by providing a spring made of a shape memory alloy to produce an attracting force and repelling force, and a shock force generation mechanism having a generator for magnetic force or electrostatic force.

CONSTITUTION: To move a moving object means 1 to the right, electric current is supplied to a generator 4 for magnetic force or electrostatic force to generate larger attracting force between the mass 1 and an inertia body 2 than the friction force operating on the mass 1, and the mass 1 receives a rightword force to move to the right. At this moment, the reaction force to the mass 1 is mitigated by a buffer spring 6 and a shape memory alloy made spring 3. Conversely to move to the left, a control current is sent to the spring 3 to heat up over the critical temperature in a short time. Then the spring 3 is reversely transformed to generates a larger elastic force than the friction force acting on the mass 1, and then the mass slightly moves to the left. The reaction force to the mass 1 at this moment is mitigated by the spring 6. On the contrary, it is possible to generate a repelling force by the generator 4 to move the object 1 to the right and attracting force by the spring 3 to move it to the left.