N719 dye adsorption on anatase TiO2 surfaces with different adsorption densities was investigated by IR-absorption spectroscopy using a multiple internal reflection technique. When the N719 dye was adsorbed on the TiO2 surface by immersing it in an N719 solution consisting of acetonitrile and tertiary-butyl alcohol, chemisorbed and physisorbed N719 dyes coexisted on the surface. The ratio of chemisorbed and physisorbed dye densities was dependent on the N719 exposure, and excessive exposure led to the generation of the physisorbed dye. Test fabrications of the dye-sensitized solar cells (DSCs) with various N719 exposures suggested that we need to optimize the dye adsorption density to achieve a higher power conversion efficiency in DSCs.