In recent years, massage is expected to be used to address the problems associated with the rapid increase in the elderly population in Japan. In order to realize better massage, we have been developing a massage robot with a multi-fingered hand that can respond to the physique of the person being massaged. The robot must be equipped with highly durable, compact, and multi-directional force-measuring sensors at its fingertips to ensure safe operation. We are developing a vibration-based force sensor that meets these characteristics. In this paper, we report on the relationship between the resonance frequency and the load in two directions on the prototype force sensor, and the verification of the estimation method of the load in two directions.