As a mode switching shift line when a sub-transmission mechanism is switched from a first-speed to a second-speed, a first mode switching shift line, which prioritizes a learning of a hydraulic pressure with which a Low brake starts to slip and a learning of a hydraulic pressure with which a High clutch starts to transmit a torque, or a second mode switching shift line, which is a shift line in a Low side with respect to the first mode switching shift line and prioritizes a fuel efficiency of an engine is selected, and the sub-transmission mechanism is switched from the first-speed to the second-speed on the basis of the selected mode switching shift line.