A vehicle seat heater (10) that is mounted to a vehicle seat (50) and provided with: a base sheet (12); and a heater wire (14) provided in said base sheet (12). Said vehicle seat heater has a reinforcing sheet (18) attached to a side part (10b) disposed in a side area (50c) of the vehicle seat (50). Opposing sections (18a) that extend in the front/back direction of the side part (10b) are provided at the edges of the reinforcing sheet (18), at least towards the front of the side part (10b). The heater wire (14) is provided in the region between said opposing sections (18a). This minimizes the incidence of heater-wire (14) breakage in the side part (10b) of the vehicle seat heater (10), said side part being disposed in the side area (50c) of the vehicle seat (50).
