The purpose of present study was to estimate the arm joint angles in front crawl swimming using the accelerometer. The subjects were four well-trained swimmers. The acceleration of the swimmer's wrist was measured using the tri-axial accelerometer, which was attached to swimmer's forearm. The arm motion under water was expressed by the arm motion model, which had three degree of freedom. Each angle of arm joints was formulated as exponential functions. The angles of swimmer's shoulder extension and elbow extension/flexion were estimated using the acceleration data of swimmer's wrist and the arm motion model of front crawl swimming. The results showed the estimated shoulder extension angle was similar to the angle calculated from videography, although it was difficult to estimate all parameters of shoulder extension and elbow extension/flexion angles. It was concluded that the measurement of swimming motion by accelerometer had the possibility to be applied as suitable method to the training of swimming.