hydraulic control apparatus includes a belt - drive cvt , a pressure regulator valve regulating the oil pressure produced by an oil pressure source , a controller programmed to develop a transmission control signal , a transmission actuator driven based on the signal , and a transmission control valve actuated by the actuator . there are provided a first oil passage for supplying an oil pressure regulated by the p . reg . v , a second oil passage for supplying the oil pressure regulated to a primary pulley cylinder chamber of the cvt and draining the oil pressure therefrom , a third oil passage for draining the oil pressure within the cylinder chamber , and a fourth oil passage downstream of the p . reg . v . the third and fourth oil passages are connected to supply an oil pressure to the cylinder chamber and establish a minimum oil pressure required for clamping the belt depending on reduction of the oil pressure within the cylinder chamber .