(57) A heat sensitive recording material comprising a support and a recording layer formed thereon, the recording layer containing (a) a diazo compound, (b) a coupling component and (c) a coloring activator, as the three main components, at least one of the three components (a) to (c) being present in microcapsules and the wall of the microcapsules being composed of a polymer formed around the material encapsulated by a polymerization of reactants. By incorporating a part of the main components in microcapsules, the shelf life of the heat sensitive recording material is greatly improved and when the wall of the microcapsules is formed by the polymerization of reactants around the material encapsulated, the reactive component in the microcapsules immediately passes through the capsule wall upon heating to cause coloration.