AbstractSome techniques of rock magnetism were tried to apply to deduce alteringtemperature of the red altered andesite rocks of Shibayama, Yashima, and Kiyama from which the specific chocolate red colored soils had been formed.Interpreting the Jn-ΔJt plots acquired by THELLIER's graduate heating method together with the results of thermomagnetic and X-ray diffraction analyses, it was Indicated that the red rocks had been formed by alteration at the temperature of 450–500°c or otherwise at higher than Curie temperature. Thus, the red altered rock specimens among which no distinct differences was noticed showed the possibility of suffering the different process or degree of alteration. Though further study especially on the oxidation state at alteration may be indispensable, fairly definite Interpretation for the process of rock weathering or soil formation could be done by Introduction of some techniques of rock magnetism.Based on the results of the studies hitherto carried out, the authors can conclude that the chocolate red colored soil of Shibayama type derived from the red Intermediates cannot be considered to have been formed under ordinary climatic weathering, and must not be confused with the soils of existing soil type but be distinguished as one belonging to a new intrazonal soil type.