The purpose of the present invention is to provide a membrane separation apparatus with which damage of the separation membrane can be prevented even when a sealing member deteriorates. This membrane separation apparatus 1 is characterized in being equipped with: a lower support 11 in which an inlet port 112a for water to be treated and a concentrate-discharging port 112b are provided; an upper support 12 in which a permeate-discharging port 122a is provided; a separation membrane 13 that is provided between the lower support 11 and the upper support 12 and is for separating the water being treated into permeate and concentrate; and a sheet-shaped elastic member 14 that is provided between the separation membrane 13 and the lower support 11 and is for sealing between the separation membrane 13 and the lower support 11 and between the lower support 11 and the upper support 12.
