We propose a method for determining grip force based on active bone-conducted sound sensing, which is an active acoustic sensing. In our previous studies, we estimated the joint angle, hand pose, and contact force by emitting a vibration to the body. We aspired to expand to an additional application of an active bone-conducted sound sensing, thus, we tried to estimate the grip force by creating a wrist-type device. The grip force was determined by using the power spectral density as the features, and gradient boosted regression trees (GBRT). Through evaluation experiments, the average error of the estimated grip force was around 15 N. Moreover, we confirmed that the grip strength could be determined with high accuracy.