Vibration in the passively-supported direction is reduced by varying the stiffness in the suspension. The magnetic suspension system using the attractive force of an electromagnet is inherently unstable in the normal direction; active control is necessary to achieve stable suspension. In contrast, it is usually stable in the lateral direction because of the edge effects in the magnetic circuits. However, damping in this direction is quite small so that vibration is easily induced. In this work, varying stiffness controls are applied to suppress the vibration. An experimental apparatus was built to examine the efficacy of the varying stiffness control. It has two electromagnets operated differentially. To adjust the stiffness in the passively-supported direction, the bias current of each electromagnet is varied simultaneously. First, the bias current is varied stepwise. The effect of the amplitude of step on vibration suppression is examined. Then, the bias current is varied continuously to avoid erroneous operations caused by noise included in the sensor signal. The efficacy of approximating the sign function by a continuous function is demonstrated experimentally.