Disclosed is a voltage regulator, which makes a low dropout regulator stop working by controlling a sampling circuit of the low dropout regulator to break in a sleep mode, and makes an output voltage of the low dropout regulator follow an output voltage of a first bias voltage generating circuit by using a first MOS transistor connected between an voltage input end and an voltage output end of the low dropout regulator in a source follower structure, and is capable of controlling an output voltage of the whole voltage regulator by a generated bias voltage applied to the first bias voltage generating circuit by a first bias current source.