A seat portion for a seat wherein the seat portion includes a panel having a rear portion to support the occupant. It is thus possible to possible to suppress variations in the base voltage of the bias supply transistor 41 in particular when the high-frequency power amplifier is at high output and improve the linearity of the high-frequency power amplifier. Such a catalyst for epoxide producing use can be produced by, for instance, fixing gold fine particles to a carrier having an acid quantity of not more than 0. , in air, heating a material, directing the heated material at the masked article, and forming a coating of the material on the article.