PURPOSE: To stabilize a speed change point during kick down by a method wherein a kick-down modulate hydraulic passage is connected to the hydraulic source port of each of a throttle valve, a throttle modulator valve, and a kick-down valve.

CONSTITUTION: During non-kick down, a throttle valve 54 and a throttle modulator valve 56 perform a pressure regulation action by means of an oil pressure, fed through an oil passage 106 from a kick-down modulator valve 82 and serving as a hydraulic source, and controls switching of a shift valve 66 by means of a throttle modulate pressure or a throttle pressure. Meanwhile, during kick down, a pressure regulating action by the throttle valve 54 is rendered ineffective, a specified pressure from the kick-down modulator valve 82 is exerted on an oil passage 114, and further exerted on a shift valve 66 through a kick-down valve 55 end an oil passage 122. A pressure regulating action by the valve 56 is also rendered ineffective, and the shift valve 66 is switched by means of a balance between a force by a specified pressure and a force by a pressure from a governor valve 62. This constitution stabilizes a speed change point during kick down and enables variation of the speed change point through the force of only a spring 102.