Nanowires (NWs) are ideal nanostructures for exploring the effects of low dimensionality and thermal conductivity suppression on thermoelectric behavior. However, it is challenging to accurately measure temperature gradients and heat flow in such systems. Here, using a combination of spatially resolved Raman spectroscopy and transport measurements, we determine all the thermoelectric properties of single Se-doped InSb NWs and quantify the figure of merit ZT. The measured laser-induced heating in the NWs and associated electrical response are well described by a 1D heat equation model. Our method allows the determination of the thermal contact resistances at the source and drain electrodes of the NW, which are negligible in our system. The measured thermoelectric parameters of InSb NWs agree well with those obtained based on field-effect transistor Seebeck measurements.