The invention relates to a steam-water separating and reheating device, in particular to a large nuclear power double-pipe bundle steam-water separating and reheating device. The invention aims to solve the problems of low efficiency and heat transfer property and complex structure of the traditional steam-water separating and reheating device of a nuclear power unit. The large nuclear power double-pipe bundle steam-water separating and reheating device comprises a shell, a two-stage reheater pipe bundle and a steam-water separation element, wherein the two-stage reheater pipe bundle comprises a group of U-shaped heat exchange pipes with fins and a group of supporting plates, the group of U-shaped heat exchange pipes with fins are coaxially arranged to form a pipe bundle, the pipe bundle sequentially passes through the group of supporting plates, the steam-water separation element comprises an upper baffle plate, a lower baffle plate, a plurality of corrugated plates and a plurality of water-drop gathering hooks, a plurality of wet steam inlets are arranged on the lower surface of the shell, a plurality of wet steam outlets are arranged on the upper surface of the shell, and a shell dewatering outlet is arranged on the lower surface of the shell. The large nuclear power double-pipe bundle steam-water separating and reheating device is used for dewetting and reheating wet steams discharged by a high pressure cylinder of a nuclear power turboset.