A drive mechanism is interposed between two members to make the members move relatively with respect to each other. At least one of the two members is guided to move linearly. The drive mechanism comprises: cam followers that are rotatably supported on one of the two members, that are arranged in the linear moving direction, and that are spaced from each other; and a cam that is rotatably supported on the other one of the two members and that is provided in its circumference with a cam groove in which the cam followers engage, the rotation axis of the cam being arranged in the direction of the linear moving direction. The two members are made to move relatively with respect to each other by driving the cam to rotate and making the cam followers engage successively in the cam groove and move in the direction of the rotation axis.