An arrangement for steering the radiation lobe of an array antenna without turning the antenna itself. The radiators of the array antenna (371, 372, 373, 374) are located in the row, and two radiators (371 , 372, 373, 374) which are equidistant from the midpoint of the row, form a radiator pair (371, 372, 373, 374). To steer the radiator lobe, the phase of the signal of one radiator in the pair (371, 373, 372, 374) is e.g. advanced and the phase of the signal of the other radiator (371, 373, 372, 374) is lagged by equivalent amount. For this aim each radiator (371, 372, 373, 374) is fed through a phase shifter comprising at least one reflection line (341, 343) and a separating element (351, 352, 353, 354). The reflection lines (341, 343) for the pair radiators (371, 372, 373, 374) are implemented by a transmission line (321, 322, 323, 324), which is shared between them. The signal to be led to one radiator (371, 373, 372, 374) is fed to one end of this transmission line (321 , 322, 323, 324), and the signal to be led to the other radiator (371, 373, 372, 374) is fed to the opposite end of the same line. In the transmission line (321, 322, 323, 324) there is a reflection point (331, 332), the place of which can be moved. Said phase changes take place by moving the reflection point (331, 332) along the transmission line (321, 322, 323, 324). For moving the reflection point (331, 332), the transmission line (321, 322, 323, 324) has one movable (331, 332) or several fixed reflection circuits. In the former case, the reflection circuits (331, 332) of the different transmission lines (321, 322, 323, 324) are slides attached to one and the same movable arm (361 ). In the latter case, one of the reflection circuits of each transmission line is activated at a time. If the number of the radiator pairs (371, 372, 373, 374) is more than one, the phase adjusting for all the radiator pairs (371, 372, 373, 374) is implemented simultaneously by the common control.