Problem is to selectively and inexpensively recover a metal ion in a liquid.Solution is a metal ion recovery device, in which a permselective membrane for selectively permeating Li is used, and on both main faces of the plate-like permselective membrane, a mesh-like negative electrode and a positive electrode are formed, respectively. This structure is provided in a treatment tank, and in the treatment tank, the permselective membrane partitions between a stock solution containing a Li ion, and a recovery solution into which Li is recovered. As the permselective membrane, lithium nitride (Li3N), Li10GeP2S12, (Lax, Liy)TiOz, Li1+x+yAlx(Ti, Ge)2−xSiyP3−yO12, and the like, which are super lithium ion conductors, can be used.