Benralizumab is a promising drug for severe uncontrolled asthma. This study aimed to clarify the effectiveness of benralizumab in a real-life setting. Subjects included 24 patients with severe type 2 asthma who received benralizumab between April 2018 and July 2019. Changes in parameters, exacerbation frequency, and oral corticosteroid (OCS) use after 4 and 24 weeks of administration were examined. The parameters included the Global Evaluation of Treatment Effectiveness (GETE) scale, Asthma Control Questionnaire (ACQ), Asthma Control Test (ACT), blood eosinophils, fractional exhaled nitric oxide (FeNO), and spirometry. The response to treatment was defined as follows: for patients with exacerbations or OCS use before treatment initiation, a reduction of ≥50% in exacerbation frequency or OCS use; and for patients without exacerbations or OCS use, an improvement of ≥0.5 in ACQ scores and ≥3 in ACT scores, or of ≥10.38% in FEV1. Twenty-one patients completed the treatment for 24 weeks. Excellent and good GETE scales and ACQ and ACT improvement were found in 67% of the patients at 4 weeks, and the effect continued until 24 weeks. The patients’ rate with exacerbations was significantly reduced compared to the previous 24 weeks before administration. In 17 patients receiving OCS, the use could be reduced or quit in 14 patients. Overall, 16 patients (76.2%) met the responder definition and could be predicted by the baseline eosinophil count and FeNO levels with the best cut-off values of 100/μL and 40 ppb, respectively. Blood eosinophil and FeNO could predict benralizumab effectiveness.