A microstrip antenna includes a substrate, a feedline, an impedance matching structure, and a patch radiator, wherein the substrate has a surface. The feedline is disposed on the surface and extends along a first axial direction. The impedance matching structure is disposed on the surface and has a first end and a second end in the first axial direction, wherein the first end is connected to the feedline. The impedance matching structure has a stepped impedance change. The patch radiator is disposed on the surface, wherein the patch radiator and the second end of the impedance matching structure are adjacent and spaced by a distance in the first axial direction, and the second end of the impedance matching structure is coupled with the patch radiator through the distance. Therefore, a bandwidth of the microstrip antenna could be increased.