A steam turbine drain structure includes a drain pocket for collecting drain water generated in a steam turbine, and a drain hole communicating with the lower side of the drain pocket. The steam turbine drain structure further includes a drain pan arranged below the exit of the drain hole and configured to collect drain water discharged from the drain hole, and a connection pipe one end of which is connected to the bottom portion of the drain pan and the other end of which is connectable to piping laid outside the steam turbine.