This paper presents a new design approach for the soft-switching resonant converter with satisfying the multiple design conditions. As an example, the FM controlled class-E resonant converter is designed. By applying the class-E inverter at the inverter part, the resonant converter works with high efficiency at high frequencies. The class-E inverter has, however, problems, which are the high peak value of the switch voltage and the difficulty of the zero-voltage switching continuation against the load variations. Additionally, there is a restriction on the peak value of the transformer voltage. In the proposed design approach, we can find the proper component values, which satisfy the multiple constraint conditions simultaneously, by full-use of the numerical computations of the converter-characteristic visualization on the parameter space. From the quantitative agreements between the experimental results and numerical predictions, the validity and effectiveness of the proposed design approach were confirmed.