A quick response vector controll method which is one of methods for controlling a speed of an induction motors (2) without a speed detector; in which a voltage of the motor is detected (6) to resolve (7, 8) into a vector component e d parallel with an exciting current component vector of a primary current and a vector component eq orthogonal to said exciting current component vector, and a frequency of the primary current is controlled (5, 9, 10, 12, 13, 15) to maintain the vector component e d at zero, while at the same time the primary current is controlled corresponding to a difference (5) between the vector component eq and the speed command signal (3).