Provided is an ultra low-power wake-up receiver capable of reducing an operating time of an analog receiver by controlling operation on/off of the analog receiver according to a clock signal from a digital receiver in an amplitude-shift keying (ASK) or on-off keying (OOK) radio receiver. The ultra low-power wake-up receiver includes: a clock generator generating a clock signal having a predetermined frequency; an operation controller controlling analog operation-on for a predetermined time according to the clock signal from the clock generator; an analog receiver maintaining an operation-on state for a predetermined time according to the analog operation-on control performed by the operation controller, and being operated off after the predetermined time; and a digital receiver being operated on while the analog receiver maintains the operation-on state