Vivaldi antenna is one of the many types of antenna implemented on ground penetrating radar (GPR). Its characteristics are pointed radiation and wide bandwidth. This study aims to design an antenna used in GPR for non-destructive test application on a transportation to check the roadway material. This Vivaldi antenna has a wide bandwidth, 1 GHz approximately, with the frequency range between 1 GHz and 2 GHz. This Vivaldi antenna design is obtained by changing few parameters of common Vivaldi antenna to fulfill its design characteristics: low cost and wide bandwidth. The antenna size is 350mm x 300mm. The simulation result shows that there is a return loss below–10 dB for 1–2 GHz frequency range, and the lowest return loss at that frequency range is around–35 dB on 1.4 GHz. This article also explains about the effect of tapered slot size changes to return loss value and frequency. When the antenna width is enlarged, the value of return loss is gets smaller in the lower frequency. Therefore, antenna bandwidth gets wider. The same happens when tapered slot size gets bigger value, the antenna working frequency switches into the lower frequency. It can be concluded that antenna bandwidth widening can be done by enlarging tapered length value and reducing tapered rate value.