To provide a photovoltaic power generating auxiliary power supply that increases power generating capacity, and is made small in size and light in weight.

A lightning rod grounding device is provided with three pieces solar cell panels 21, 22, 23; a linking mechanism that links the panels in such a way that the solar cell panels 21, 22, 23 can be stacked on each other or extended, a connector 30 that is coupled to a charging terminal of a mobile phone; and a circuit that conducts electric power that is outputted from the solar cell panels 212, 22, 23 to the output terminal of the connector 30. By extending the solar cell panels 21, 22, 23, a larger light-receiving area is secured so that large power generating capacity can be acquired. Also, this device is made small in size and light in weight, because neither a secondary battery nor a step-up circuit is required; and when it is not in use, the solar panels 21, 22, 23 are contracted into a compact shape by stacking them on top of each other.