An addition-curable organopolysiloxane resin composition having, in a state of cued body, a hardness of 60 to 100 at 25 degree C and 40 to 100 at 150 degree C as measued in accordance with the provisions of ASTM D2240-86, said composition comprising: (A) 100 parts by weight of an organopolysiloxane resin comprised of at least alkenyl groups and phenyl groups; (B) 10 to 50 parts by weight of an organooligosiloxane comprised of at least alkeyl groups and phenyl groups; (C) 20 to 100 parts by weight of an organohydrogenoligosiloxane or organohydrogenpolysiloxane; and (D) an addition-reaction catalyst in a catalytic quantity; an optical material that is comprised of a cured body producted from aforementioned components (A), (B), and (C) and posseses the aforementioned characteristics.