Provided is a discrete filter capable of increasing degree of freedom of design including a DC gain. A sampling mixer (100) includes: a control signal generation unit (104) which generates a control signal including an SO signal; a Ch (6) which successively integrates reception signals sampled by an LO signal frequency as discrete signals; a plurality of Cr (7, 8) which successively integrate discrete signals at a timing based on the control signal; Cb (15) which alternately integrates the discrete signals successively integrated by the respective Cr (7, 8); and a gain control capacitance unit (110) which has gain control capacitors (44, 45, 46) connected in parallel to the respective Cr (7, 8) and integrating the discrete signal and a reset switch (47) for resetting the discrete signal of the gain control capacitors (44, 45, 46) integrated in the past, upon connection between one end of Cr (7) and Cb (15).