The invention relates to a prestressed anchorage device and a tensioning device. The prestressed anchorage device comprises fixed ends, tensioning ends, tensioning parts and fixed parts; the fixed ends and the tensioning ends are connected to the bridge bottom faces; each fixed end comprises a fixed plate and a fixed block, and each fixed block is provided with multiple fixed holes which are through holes; each tensioning end comprises a tensioning plate and a tensioning block, and each tensioning block is provided with multiple tensioning grooves which are through grooves; the length of each fixed plate is the same as that of each tensioning plate, the number of the fixed holes is the same as that of the tensioning grooves, and the positions of the fixed holes correspond to those of the tensioning grooves; one end of each tensioning part penetrates through the corresponding fixed hole and is connected to the corresponding fixed block of the corresponding fixed end through the corresponding fixed part; the other end of each tensioning part penetrates through the corresponding tensioning groove and is connected to the corresponding tensioning block of the corresponding tensioning end through the corresponding fixed part in a clamped mode. In this way, prestress of a bridge can be conveniently increased, the structure is simple, and construction is convenient.