Surface morphology of oxacyanine dye (OC) suddenly changes in mixed Langmuir-Blodgett films composed of OC, arachidic acid, and methyl arachidate when the OC fraction becomes more than 30 mol %. The agglomerates of OC show a ring structure just like a rubber band. The diameter and the shape of the "rubber band" change with different OC fractions, and microcrystalline domains appear when J-type aggregates are formed. The morphological change of the surface monolayer is well-correlated with a change in the electroabsorption spectra of the OC chromophore.