A movement with two leaf springs can be modified to one with four leaf springs by replacing the each of midpoints of upper and lower springs, respectively, with reinforcing plate. Even so, the ideal point whose displacement remains unchanged sticks on the midpoint of the reinforcing plate, regardless of the loading position. The above is undisturbed by dimensional errors as far as the symmetry of the movement is kept. The dimensional errors, however, bring the constant error rate of displacement at the ideal point, resulting in the error of mass to be measured by a balance using the movement. Authors discussed in this paper the influences of the dimensional errors in length and thickness of the four leaf springs on the error rate of displacement. Followings are clarified theoretically, experimentally and by FEM ; (1) Around 3/4 and 3/8 of the rate of dimensional error in thickness and length, respectively, contribute to the error rate of displacement. (2) The error rates of displacement are proportional to the difference between the dimensional errors in thickness of two springs, and are proportional to the difference between those in length of outside (or inside) of the two springs.