A method for predicting the prognosis of breast cancer to provide information necessary for predicting the prognosis of a breast cancer patient, the method comprising the steps of: (a) measuring a mRNA expression level of UBE2C (Ubiquitin-conjugating enzyme E2C), TOP2A (Topoisomerase 2 alpha), RRM2 (ribonucleotide reductase M2), FOXM1 (Forkhead box M1) MKI67 (Marker of proliferation Ki-67) and a BTN3A2 (Butyrophilin subfamily 3 member A2) from a biological sample obtained from the breast cancer patient, respectively; (b) normalizing the mRNA expression level measured in the step (a); (c) evaluating the size of a tumor and a pN-stage in the breast cancer patient; (d) calculating a numerical value by putting a normalized value obtained in the step (b), and the size of the tumor and the pN-stage in the step (c) into the following Equations 1 and 2 Unscaled BCT score U − BS = a * Δ Ct _ UBE 2 C + b * Δ Ct _ TOP 2 A + c * Δ Ct _ RRM 2 + d * Δ Ct _ FOXM 1 + e * Δ Ct _ MKI 67 + f * Δ Ct _ BTN 3 A 2 + g * Tumor _ size cm + h * pN 0 or 1 BCT score = 0 if 0.8 * Unscaled BCT score U − BS − 13.71 < 0 BCT score = 0.8 * U − BS − 13.71 if 0 ≤ 0.8 * U − BS − 13.71 ≤ 10 BCT score = 10 if 0.8 * U − BS − 13.71 > 10 wherein the value of the gene used for predicting the effectiveness of chemotherapy is a normalized mRNA expression value calculated using a standard gene; The tumor size is a value determined as the long axis length of the tumor and the pN is a value determined according to the pathological judgment of a lymph node metastasis, Wherein a a is 0.16 to 1.09, b is 0 to 0.71, c is 0 to 0.53, d is 0 to 0.57, e is 0 to 0.35, f is -1.02 to 0, g is 0.25 to 1.52 and h is 0.19 to 2.25; and (e) predicting that the greater the value calculated in the step (d) is, the poorer the prognosis is. (a) measuring a mRNA expression level of UBE2C (Ubiquitin-conjugating enzyme E2C), TOP2A (Topoisomerase 2 alpha), RRM2 (ribonucleotide reductase M2), FOXM1 (Forkhead box M1) MKI67 (Marker of proliferation Ki-67) and a BTN3A2 (Butyrophilin subfamily 3 member A2) from a biological sample obtained from the breast cancer patient, respectively; (b) normalizing the mRNA expression level measured in the step (a); (c) evaluating the size of a tumor and a pN-stage in the breast cancer patient; (d) calculating a numerical value by putting a normalized value obtained in the step (b), and the size of the tumor and the pN-stage in the step (c) into the following Equations 1 and 2 Unscaled BCT score U − BS = a * Δ Ct _ UBE 2 C + b * Δ Ct _ TOP 2 A + c * Δ Ct _ RRM 2 + d * Δ Ct _ FOXM 1 + e * Δ Ct _ MKI 67 + f * Δ Ct _ BTN 3 A 2 + g * Tumor _ size cm + h * pN 0 or 1 BCT score = 0 if 0.8 * Unscaled BCT score U − BS − 13.71 < 0 BCT score = 0.8 * U − BS − 13.71 if 0 ≤ 0.8 * U − BS − 13.71 ≤ 10 BCT score = 10 if 0.8 * U − BS − 13.71 > 10 wherein the value of the gene used for predicting the effectiveness of chemotherapy is a normalized mRNA expression value calculated using a standard gene; The tumor size is a value determined as the long axis length of the tumor and the pN is a value determined according to the pathological judgment of a lymph node metastasis, Wherein a a is 0.16 to 1.09, b is 0 to 0.71, c is 0 to 0.53, d is 0 to 0.57, e is 0 to 0.35, f is -1.02 to 0, g is 0.25 to 1.52 and h is 0.19 to 2.25; and wherein the value of the gene used for predicting the effectiveness of chemotherapy is a normalized mRNA expression value calculated using a standard gene; The tumor size is a value determined as the long axis length of the tumor and the pN is a value determined according to the pathological judgment of a lymph node metastasis, Wherein a a is 0.16 to 1.09, b is 0 to 0.71, c is 0 to 0.53, d is 0 to 0.57, e is 0 to 0.35, f is -1.02 to 0, g is 0.25 to 1.52 and h is 0.19 to 2.25; and (e) predicting that the greater the value calculated in the step (d) is, the poorer the prognosis is.