An automatic-transmission hydraulic pressure supply system includes a low-pressure hydraulic pump supplying low hydraulic pressure to a first low-pressure line, a low-pressure regulator valve recirculating through a first recirculation line a portion of the hydraulic pressure supplied through the first low-pressure line to regulate the hydraulic pressure of the first low-pressure line, and supplying the regulated hydraulic pressure to a low pressure portion through a second low-pressure line, a high-pressure hydraulic pump receiving a portion of the hydraulic pressure of the first low-pressure line, increasing and supplying the increased hydraulic pressure to a high pressure portion through a high-pressure line, and a high-pressure regulator valve recirculating a portion of the hydraulic pressure supplied through the high-pressure line through second and/or third recirculation lines, and supplying the regulated hydraulic pressure to the high pressure portion.