Antioxidative activities, total phenolic compounds and the sulforaphane contents of cooked broccoli extracts were studied. Total phenolic compounds were determined to be 0.96 mg/g(flower) and 0.76 mg/g(stem) in fresh broccoli extracts. The total phenolic compounds of cooked broccoli extracts showed 0.92 (1 min), 0.79 (3 min), 0.67 (10 min) mg/g when a boiling process was used and 1.27 (1 min) mg/g when a steaming process was used. In the DPPH assay, the steam process showed the highest free radical scavenging capacities. Sulforaphane has been of increasing interest in the nutraceutical and phamaceutical industries due to its anti-cancer effect. Sulforaphane was isolated from fresh and boiled, steamed broccoli using dichloromethane as an extract solvent. The sulforaphane contents of fresh broccoli were higher in the flower (14.78 mg/kg) than in the stem (6.16 mg/kg). The sulforaphane content dramatically decreased after the boiling ($100{pm}2^{circ}C$) or steaming ($100{pm}2^{circ}C$) processes were used.