Olivine-orthopyroxene-andesite in Tobe Town, Ehime Prefecture, Japan has been investigated based on geology and petrology. It intrudes into the Mannen altered andesite but it has not undergone hydrothermal alteration. The olivine-orthopyroxene-andesite contains Mg-rich olivine and orthopyroxene and Cr-rich chromite. It is a high-Mg andesite (HMA) based on petrography and bulk rock chemistry. From the effect of the hydrothermal alteration the age of the intrusion is inferred to be immediately after the hydrothermal alteration of the Mannen altered andesite.