Ultra-compact mobility is leveraged to streamline transportation. This mobility makes it easy to drive vehicles on narrow roads because it makes them light in weight. However, there is a possibility that ride comfort is degraded because ultra-compact mobility often means that equipment must be made simple so that it can be miniaturized. To improve ride comfort against vertical vibration, we previously proposed an active seat suspension mounted on the seat section of a vehicle. This active suspension makes it possible to control vibration actively by means of a voice coil motor. We examined the reduction in vibration with the suspension when entering rough roads and developed a practical control method. Motor characteristics, e.g. motor stroke, thrust variability, and voltage capacity, are important factors for reducing vibration. In particular, ride comfort is affected when going over bumps. Therefore, in this paper, the voice coil motor was evaluated by using electromagnetic field analysis. Moreover, the efficiency of vibration control was investigated in a simulation in which voltage capacity and nonlinearity of thrust were considered.