A hydraulic pressurizer system 30 comprises a drive source (an engine 2 and a motor generator 4), which drives a hybrid vehicle 1, a mechanical oil pump 20, which is driven by the drive source, an electrical motor 22, which is activated by a 12V battery 24, an electrical oil pump 21, which is driven by the electrical motor 22, and a control unit 15, which activates the electrical motor 22. The pressurizer further comprises a ratio-change mechanism 7, which is activated by hydraulic oil supplied by the mechanical oil pump 20 and by the electrical oil pump 21 to establish a speed change ratio, at which the rotational driving force of the drive source is transmitted to wheels 8 with a rotational speed change. The control unit 15 memorizes a characteristic value CV, which is specified from the temperature of the hydraulic oil and from the rotational speed of the electrical motor 22, and a threshold value NTH2 for the rotational speed Np of the electrical motor 22, which threshold value corresponds to the characteristic value CV. While the control unit 15 is executing a so-called idling-stop control, it cancels the idling-stop control if the rotational speed Np of the electrical motor 22 reaches the threshold value NTH2.