Ocean thermal energy conversion has gained focus generating stable electric power while providing additional benefit. By some research, it is shown that using a double-stage Rankine cycle is theoretically more efficient than a single-stage Rankine cycle. Moreover, several studies have been made on the experimental study of a double-stage Rankine cycle. But the comparison of theoretical result with experimental result has never been studied so far. In this research, it was demonstrated a double-stage Rankine cycle experimental plant, and attempted to compare experimental result with theoretical result.