Anti-parallel stacked lamellar films of N-methyl-4-octadecyloxystilbazolium arylcarboxylates (C18O-Stz(+)X(-)) were found to undergo reversible layer expansion and shrinkage along the c-axis on the glass plates under alternative illumination at lambda > 350 and 254 nm. The stacked lamellar units changed in length according to the phase transition of the lamella structure induced by the photochemical [2+2] cyclodimerization and cycloreversion of C18O-Stz(+)X(-) in the organized assembly.