Abstract: A dehydrating apparatus, a dehydration system, and a dehydration method have improved membrane performance. The dehydrating apparatus 1 includes, in a dehydrating apparatus body, a water separation membrane module 10 in which a water separation membrane having at least one flow path extending in the up and down direction to cause a liquid to pass through is provided with a liquid inlet at the bottom thereof and a liquid outlet at the top thereof; and a shell 11 defined by the outer surface of the water separation membrane module and the inner wall of the dehydrating apparatus body. A heater 12 is provided in the shell near the liquid outlet, and a connection port 14 for connection with a pressure reducing device 13 is provided in the shell near the liquid inlet. As the liquid rises in the water separation membrane, water in the liquid permeates the water separation membrane and moves into the shell, by which the liquid is dehydrated.