It is an object of the present invention to provide a sampling mixer and a receiver, capable of optimizing a sampling rate of an output signal in response to a fractional band of a modulation band with respect to an RF frequency of the received signal. A sampling mixer of the present invention, includes a history capacitor 6 for integrating a received signal that is converted in terms of current in a continuous time, rotation capacitors 7 to 14 for repeating an integration and a discharge of an input signal, a digital controller 104 for controlling integration periods of the rotation capacitors 7 to 14, and a controlling portion 105 for controlling discharges of the rotation capacitors 7 to 14, wherein the number of the rotation capacitors 7 to 14 connected at a time to a buffer capacitor 15 is switched in answer to a fractional band of the modulation band with respect to a RF frequency. As a result, the decimation ratio of the sampling rate can be varied, and the quantization noise generated in the AD conversion can be reduced.