EarthCARE (Earth Clouds, Aerosol and Radiation Explorer) project is a candidate of the ESA (European Space Agency) Earth Explorer Core Missions. There are many uncertainties mainly caused by aerosols, clouds and their interaction with radiation in predictions of climate change using numerical models. EarthCARE will provide vertical and horizontal distributions and physical characteristics of clouds and aerosols, and also provide the Earth radiation budget. EarthCARE is the joint proposal between ESA, National Space Development Agency of JAPAN (NASDA) and Communications Research Laboratory (CRL). The Phase-A study is going on. The EarthCARE satellite has five sensors, Cloud Profiling Radar (CPR), ATmospheric LIDar (ATLID), Multi-Spectral Imager (MSI), Broad Band Radiometer (BBR) and Fourier Transform Spectrometer (FTS). NASDA is studying FTS design. Main objective of EarthCARE FTS is to provide spectrally resolved outgoing radiance. This spectrum has many useful signatures from the surface/cloud/aerosol/water which can not get from spectrally integrated measurement. Another objective of EarthCARE FTS is a compact Michelson interferometer, which covers from 5.6 µm to 25 µm with 0.5 cm-1 spectral resolution. The FOV (Field Of View) is 10km so that the data can be used in conjunction with BBR.