Powdery fullerene is milled in an oxygen atmosphere, whereby mechanical impacts are applied to the fullerene and a carbon cage of the fullerene is dynamically distorted to the extent that an energy for conversion of atmospheric oxygen to a singlet excited state is accomplished from the distorted carbon cage to atmospheric oxygen. Singlet oxygen, i.e. an efficient oxidant in various industrial fields, is generated by solid-state reaction under stable conditions without necessity of photo-irradiation. The singlet oxygen also enables efficient oxidation of fullerene itself.