In this paper, we report on the structure and hydrogen gas sensing properties of polystyrene palladium nanowire composites. Granular palladium nanowires (with 250 nm diameter) have been electrodeposited on Highly Oriented Pyrolytic Graphite (HOPG). In order to measure the electrical response of the sensor the nanowire were transferred to an, insulating polystyrene surface. Polystyrene thin films with the thickness of about 150 nm were formed on a glass microslide by a dip-coating technique from a chloroform solution. Silver microelectrode pads were patterned on the surface of the nanocomposite by shadow masking technique. All stages of sensor device fabrication and its mechanism were monitored with application. of atomic force microscopy technique (contact, non-contact, and force modulation modes).