A body-building device including a base body, a swing mechanism and a supporter is provided. The base body is used to support the whole body-building device. The swing mechanism is installed on the base body to enable 360-degree rotation in the circumferential direction or swing to any angle off the central axis of the base body. The supporter is installed at an upper end of the swing mechanism and makes direct contact with human body. With force applied by human body, it drives the swing mechanism to rotate or swing, while the swing mechanism generates a corresponding reset force during swing, thus enabling body building. Fitness methods are also provided.