The purpose of this study was to compare differences in the main food components of quinoa (Chenopodium quinoa Willd.) cultivated in Hongcheon after steaming, boiling, and roasting. Among the general components, crude protein, fat, and ash content were the highest in raw quinoa. Dry matter and carbohydrate content was the highest in steamed quinoa, while total dietary fiber content was highest in roasted quinoa. Total amino acid contents were the highest in boiled quinoa and lowest in steamed quinoa. Fatty acid content was highest in raw quinoa and lowest in boiled quinoa. The mineral (calcium, potassium, and phosphorus) and vitamin content was most enriched in raw quinoa, while iron, magnesium, zinc, and manganese were highest in boiled quinoa. For free sugars, the fructose and sucrose levels were highest in raw quinoa, while glucose level was highest in roasted quinoa. The water-soluble vitamin and free sugar contents were lowest in boiled quinoa. In summary, nutritional levels of vitamins vulnerable to heat and unsaturated fatty acids decreased after cooking with heat, while those of amino acids and saturated fatty acids increased after cooking with heat, although there were variables based on different cooking methods.