To solve the problem that it is difficult to synchronously present main information and related information when a related information providing device such as an information terminal is to present information related to the main information such as a broadcast program and the related information which cannot be received in a main information presenting device such as a television receiver.

A related information providing system includes: operation signal acquiring means for acquiring an operation signal of a main information presenting device; main information identification means for specifying main information which the main information presenting device presents on the basis of the operation signal and outputting the main information as a main information identification signal; related information acquiring means for acquiring the related information related to the main information; related information accumulating means for accumulating the related information; related information extracting means for extracting the related information for presentation, which is made to correspond to the main information identification signal, from the related information; and related information presenting means for presenting the related information for presentation.