The invention provides a vacuum circuit breaker. A raised installing seat (5) is arranged at the middle portion of the inner wall of an insulation sleeve (1) of the vacuum circuit breaker, a guide sleeve (3) is connected with the installing seat (5), a positioning hole in the guide sleeve (3) is sleeved with the lower end of a vacuum arc-extinguishing chamber (2), the upper end of the vacuum arc-extinguishing chamber (2) is connected with an upper support (4), and the upper support (4) is connected with the inner wall of the insulation sleeve (1). The vacuum circuit breaker plays the supporting effect on the vacuum arc-extinguishing chamber and the limiting effect on the position of the vacuum arc-extinguishing chamber, shake of the vacuum arc-extinguishing chamber in the insulation sleeve is avoided, and the stability of the installed vacuum arc-extinguishing chamber is effectively improved. Meanwhile, a lower support for the vacuum circuit breaker is omitted, attached parts are simplified, the vacuum arc-extinguishing chamber is quick and convenient to install and dismount, and the working efficiency of the vacuum circuit breaker is obviously improved.