On day 6, convalescent plasma was obtained from a male donor in his 20s who had recovered from COVID-19 for 18 days. He was diagnosed as COVID-19 presenting fever, cough and pneumonia however, showed complete recovery and serial PCRs for SARS-CoV-2 were all negative after hospital discharge. Donor screening and plasma collection were performed as mentioned above in the Case 1. OD ratio for IgG was 0.532 and the plasma was administered to the patient in the same way as Case 1. There was no adverse reaction during the plasma transfusion. Leukocytosis and lymphopenia were immediately recovered after convalescent plasma infusion. On day 9, the density of bilateral infiltration on chest X-ray much improved with increased PaO2/FiO2 to 230. The level of CRP and IL-6 also recovered to the normal range (Figs. 3 and 4). SARS-CoV-2 was quantified by rRT-PCR; the value of Ct changed from 20.51 on day 5 to 36.33 on day 9 after plasma infusion (Fig. 3). The patient is successfully extubated and discharged from the hospital on day 24. SARS-CoV-2 was negative after day 20.