A sintered body includes cubic boron nitride grains as hard phase grains, and has a thermal conductivity of not less than 15 W·m−1·K−1 and not more than 40 W·m−1·K−1, for cutting a nickel-based heat-resistant alloy formed of crystal grains having a fine grain size represented by a grain size number of more than 5 defined by ASTM standard E112-13. A cutting tool includes this sintered body. Accordingly, the sintered body having both high wear resistance and high fracture resistance, as well as the cutting tool including the sintered body are provided.