To issue a correct time stamp using a clock which has an independent power source and can not be operated from the outside.

A time stamp device 10 is provided with a local clock part which can not be operated from the outside except when initializing a time, and a time stamp processing part. A local clock part equipped with an independent power source generates a time from fixed-interval oscillation signals generated by an oscillation means when receiving the supply of a power from the power source, and outputs transmission data including the time information at fixed intervals. The time stamp processing part acquires the time information from the received transmission data, and transmits the acquired time information to a time audit station system 70, and receives and stores time audit certificate data. When a time stamp request is received from a client terminal 80, and a time acquired when receiving the request is within a term of validity acquired from the stored time audit certificate data, the time stamp is generated based on the time.