To provide a conjugate fiber structure capable of producing flame-proof and protective clothes excellent in wearing feeling (e.g. hygroscopic property or moisture permeability), being lightweight and comfortable and having high flame-resistance and to provide a method for producing the conjugate fiber structure.

The conjugate fiber structure is formed by impregnating an expandable nucleating agent into a fiber, expanding the fiber to provide a wholly aromatic polyamide foamed fiber in which closed minute pores are formed in the interior of the fiber, forming a fiber structure from the foamed fiber and arranging the fiber structure on an inner layer side of the fiber structure containing ≥60 wt.% wholly aromatic polyamide fiber.