To provide a method for producing a modified-sulfur-containing material, which method can produce the modified-sulfur-containing material capable of utilizing general and industrial wastes as an aggregate therefore, excellent in mechanical properties, water barrier properties, ignition resistance, and resistance to sulfur oxidation bacteria, and useful as a civil engineering and building materials efficiently with ease of reaction control, and is suited for industrail mass-production and to provide the modified-sulfur-containing material produced thereby.

The method comprises the steps of: continuously feeding molten sulfur and a sulfur modifying agent at a specified ratio into an agitation-pipe-fitted line mixer provided in a heat-insulating tank, allowing the molten sulfur and the sulfur modifying agent to be continuously melt-mixed and to stay in the line mixer at 130-160°C to obtain the flowable modified sulfur having a viscosity of 0.05-3 Pa s (at 140°C), transferring the modified sulfur kept in a flowable state to a batch mixer, mixing a raw material containing the flowable modified sulfur and an aggregate, and cooling and solidifying the raw material.