We propose a new type of body twist measurement sensor using a 3-axis acceleration sensor and 3-axis magnetic sensor that may be applicable to sports form measurement. To measure the body twist angle, we combined the 3-axis acceleration vector and 3-axis magnetic vector by applying the singular-value decomposition technique. PSoC was used as an elemental test for the developed measurement sensor. To confirm the measurement of body twist angle, we compared it to that of several skilled baseball batters. The results suggest that the proposed method would be useful for estimating body twist angle.