This study presents a novel beam-scanning ground-penetrating radar (BS-GPR) system based on a wide-angle beam-scanning antenna array, aimed at extending the lateral detection range and improving the imaging fidelity without increasing the size of the transceiver antennas. The BS-GPR comprises a signal transceiver, a wide-angle beam-scanning antenna array for transmission and a bowtie antenna for reception. Unlike conventional commercial ground-penetrating radar (GPR), the transmitting signal of the wide-angle beam-scanning antenna array designed in this study can cover a fan-shaped region of ±90°, enabling the detection of abnormal targets outside the rectangular region directly below it. In field tests on air and sand, the BS-GPR proposed in this study can detect anomalous targets in the 55° and 30° directions, respectively. In brief, this study confirms the effectiveness of the wide-angle beam-scanning antenna array for extending the lateral detection range of GPR.