To solve the problem that Li produced after reaction is harmful to the human body in a boron neutron capture therapy, which is a cancer therapy, in which an anticancer therapeutic agent prepared by adding a compound comprising 10B to a cancer affinity group is fed into cancer cells and the cancer cells are selectively destroyed by α-rays generated in a nuclear reaction by irradiating thermal neutron beams.

The anticancer therapeutic agent prepared by adding the cancer affinity group to a fullerene including 10B or 6Li is used as the therapeutic agent for the neutron capture therapy. The safety characteristics of the neutron capture therapy are enhanced, as 10B or 6Li is included in the fullerene highly safe to the human body.