A hydraulic pressure supply system of an automatic transmission may generate low hydraulic pressure and high hydraulic pressure using oil stored in an oil pan and may supply the low hydraulic pressure and the high hydraulic pressure respectively to a low pressure portion and a high pressure portion. In the hydraulic pressure supply system, a low-pressure hydraulic pump pumping the oil stored in the oil pan and generating the low hydraulic pressure and a high-pressure hydraulic pump changing the low hydraulic pressure supplied from the low-pressure hydraulic pump into the high hydraulic pressure and supplying the high hydraulic pressure to the high pressure portion may be integrated as one hydraulic pump.