A method of screening a novel BAFF suppressor or inhibitor. More specifically speaking, a method which comprises adding a combination of TPA with ionomycin and/or an anti-CD3 antibody to a cultured human cell to thereby induce the production of BAFF by the cell; a method of screening a substance capable of suppressing the expression or activity of BAFF which comprises adding a test substance to a BAFF-production system prepared by adding a combination of TPA with ionomycin and/or an anti-CD3 antibody to a cultured human cell and measuring the expression amount and/or the activity of BAFF in the BAFF-production system; and a BAFF production inducer for a BAFF-producing cell which contains a combination of TPA with ionomycin and/or an anti-CD3 antibody.