A voltage regulator includes an integrated circuit, a first power supply circuit, and a second power supply circuit. The integrated circuit includes a first core through which passage of current is continued in a power-saving mode, and a second core through which passage of current is halted in the power-saving mode. A determination unit determines whether operational status of the second core is a predetermined state that increases consumed current of the second core. A detecting unit detects a second DC voltage output from the second power supply circuit when the determination unit determines the operational status of the second core to be the predetermined state. A voltage adjusting unit adjusts the second DC voltage such that difference in voltage between the detected second DC voltage and a required voltage of the second core is equal to or less than a predetermined specified voltage difference.