A control device is applied to a base of an umbrella stem. A buckle sits in the base whose upper portion sets a controlling device controlled by the buckle and whose lower portion radially disposes a spool disk. The peripheral wall of the spool disk having ratchets defined thereon is embraced by a spool groove. Two ends of a spiral spring are respectively fixed to the base and the spool disk to generate an elastic force driving the spool disk's rotation. A shift block positioned under the base of the controlling device has a continuous torsion to contact the spool disk and clasp the ratchets. A disk cord provides one end fixed on the spool disk and wound around the spool groove and the other end penetrating the controlling device and the base to join an upper accommodation of the umbrella.