It has been found that Spi-B, in cooperation with IRF-7, induces type I IFN production. This invention is based on the finding, and provides a type I IFN production inhibitor comprising an antisense nucleic acid or siRNA against Spi-B, or an expression vector capable of expressing the same； a screening method for a substance capable of inhibiting type I IFN production, comprising selecting a substance that suppresses the expression or function of Spi-B as a substance capable of inhibiting type I IFN production； and a type I IFN production inducer comprising an expression vector capable of expressing Spi-B and an expression vector capable of expressing IRF-7 in combination, and the like.
