A voltage-switching regulator with built-in voltage-switching module is provided, which is capable of supplying a terminal voltage to a memory unit operating under DDR (DRAM of Double Rate) mode. The voltage-switching regulator is implemented as a single IC chip with a built-in voltage-switching module, and is capable of generating a terminal voltage in response to an input reference voltage and transferring the terminal voltage via a transmission logic line to the memory unit operating under DDR mode. The terminal voltage is pulled up when the voltage-switching module supplies a drive current and is pulled down when the voltage-switching module supplies a sink current. This allows the memory unit to be operated under DDR mode.