[en] The Heusler type compounds Fe_3-xV_xSi were prepared by arc melting in the concentration range between x=0 and x=1. The samples were characterized by a powder X-ray diffraction method and EDXA. The thermoelectric properties such as the thermal diffusivity, electrical resistivity, and Seebeck coefficient were measured in the temperature range from 300 to 1073 K. The thermal conductivities of Fe_3-xV_xSi were evaluated from the heat capacity, experimental density, and thermal diffusivity measured by a laser flash method. A strong vanadium concentration dependence is shown in the thermoelectric power (TEP) of Fe_3-xV_xSi. The temperature and vanadium concentration dependences of the thermoelectric properties of Fe_3-xV_xSi were studied