A stick-used stageless adjusting device for both left-handed and right-handed users to conveniently adjust the length of the stick. The stick is formed by an upper fitting tube and a lower fitting tube fitted into the upper fitting tube. The stageless adjusting device is disposed at top end of the lower fitting tube and includes a movable body and a brake body. The movable body includes two conic bodies and a thread rod connected between the conic bodies. The conic faces of the conic bodies are opposite to each other. The brake body is formed with an annular groove on outer circumference for a rubber ring to insert therein and composed of two semicylindrical halves. Each half is disposed with a thread for screwing with the thread rod of the movable body. When counterclockwise or clockwise rotating the lower fitting tube, the two halves of the brake body are outward stretched by the conic faces of the conic bodies to lean against the inner circumferential wall face of the upper fitting tube so as to firmly fix the lower fitting tube with the upper fitting tube.