In this paper, a description is given of the method for the miniaturization of a branch-line coupler. The procedure on which the principle of decreasing the geometric dimensions of the device is based consists in replacing the quarter-wavelength segments of the microstrip transmission line with structures having similar characteristics in a certain frequency band as the replacement segment. Using the program of three-dimensional electrodynamic analysis, the frequency characteristics of the device were obtained. Using a standard method of manufacturing printed circuit boards, a prototype was produced and its characteristics were measured, which confirmed the operability of the device and the method as a whole.