To enable a PC rail tie and a construction method using it to be able to endure an extended period of use as a construction beam even when repeated loads are imposed by passage of a train.

A PC rail tie doubling as a crossbeam is used as the crossbeam of the construction beam by connecting extension blocks (2) to both ends, and is used as a PC rail tie (1) on a track bed by removing the extension blocks (2). Then a coupler (10) is connected to the end of a PC steel bar (11) of the PC rail tie, and a PC steel bar (12) is added and connected to the coupler. Then the extended PC steel bar (12) is inserted through an extension block (2), and the extended PC steel bar (12) is fixed at the end surface of the extension block or at the inside of the extension block.