Abstract: A fixation structure of a sleeve tool is provided and includes a universal joint and a universal socket. The universal joint has a surface and a universal joint hole thereunder. The universal joint hole holds therein a spring and a ball. The universal joint has a radial length including a distance by which the ball protrudes from the surface. The universal socket has a connection hole for receiving and engaging with the universal joint and has an inner side. A recess is disposed under the inner side of the universal socket. The connection hole has a hole diameter. The ratio of the radial length to the hole diameter is greater than 0.902 to prevent the ball from retracting completely into the recess even when a user pulls the universal joint 20 by hand, thereby preventing the universal joint from escaping from the connection hole of the universal socket.