We have fabricated floating-gated carbon nanotube field-effect transistors (CNTFETs). Au floating dots in the device are expected to act as charge storage nodes. The fabricated floating-gated CNTFETs clearly exhibited memory effect. Furthermore, single-electron memory was demonstrated based on floating-gated CNTFETs. Quantized shifts in the threshold voltage as a function of charging voltage and retention time were clearly observed. The quantized characteristics are attributed to the effect of single hole charging in the Au floating dots.