We have successfully carried out manipulation and visualization of carbon nanotubes in water under an optical microscope. We employed a quenching observation method  where intensity of fluorescent dyes around CNTs is decreased due to the energy transfer. By the quenching observation method, CNTs can be observed continuously for a long time by adding new fluorescent reagent after fluorescence photobleaching. However, we have to adjust its density around CNTs and it is extremely difficult to control proper condition of the reagent. Hence we built up a supplying system of fluorescent reagent in a microfluidic chip. We have found that a porous structured of PDMS could absorb fluorescent reagent as a carrier and supply reagent in high and equivalent density for a long time. In experiment, by using a micro-stirrer, we could mix a different couple of fluids uniformly and succeeded in controlling density of fluorescent reagent. Also, we have applied dielectrophoretic force for trapping of CNTs. The material for electrodes is ITO (Indium Tin Oxide). ITO is suitable for manipulation and observation of CNTs under an optical microscope because of its high conductive property and good transparency. In experiment, we trapped and observed CNTs by using quenching on the chip and confirmed that the fluorescent image of the CNTs was clearer than the bright-field image of them.