To easily and efficiently decompose dioxins in a dioxins-containing solid matter, such as soil, bottom mud, or sludge, under atmospheric pressure at a relatively low temperature with a simple apparatus.

A treatment method for a dioxins-containing solid matter is provided, by which a solid matter containing dioxins and organic substances is ground and heated to 101-200°C to decompose dioxins. A treatment apparatus for a dioxins-containing solid matter is also provided, which comprises a grinding means for a solid matter containing dioxins and organic substances and a heating means for heating the ground solid matter or the solid matter under grinding to 101-200°C. A solid matter, such as soil, bottom mud, or sludge, contains nature-derived organic substances, such as protein, in a high amount; and when these substances are decomposed under heating at 101-200°C, a substance, e.g. ammonia, capable of decomposing dioxins is generated, thereby decomposing dioxins in the solid matter.