A flexible printed circuit board (PCB) has stretchability and durability. The flexible PCB includes: a first polymer substrate having flexibility, stretchability, or elasticity; a second polymer substrate having flexibility, stretchability, or elasticity; a conductive track disposed between the first and second polymer substrates and including metal nanowires; and a cured silane coupling agent which bonds the conductive track to at least one of the first and second polymer substrates.