The invention concerns a simulated moving bed (SMB) separation device and process comprising a column, beds A.sub.i of adsorbent separated by plates P.sub.i with a single distribution and extraction network for fluids, in particular feed F, desorbant D, raffinate R and extract E, and a plurality of two-way valves for distribution of said fluids, said valves being limited in number and in particular with dimensions that are smaller than in the prior art. According to the invention, the column is divided into a plurality of sectors S.sub.k with 2 superimposed plates, each sector S.sub.k comprising an external principal bypass line L.sub.k connected to each plate P.sub.1 of S.sub.k via a large diameter plate valve V.sub.1 and an external secondary bypass line M.sub.k comprising a small diameter valve V.sub.Mk connected to the adjacent sector S.sub.k-1. Each line L.sub.k comprises a flow limitation means, and is connected to each of the fluid networks F, D, R, E via a single large diameter valve for sequential supply or withdrawal of the corresponding fluid F, D, R or E to or from the sector Sk under consideration.