Negative electrode foil and positive electrode foil having an oxide coating layer formed on the surface thereof with a separator, the separator containing a binder constituted of a compound having a vinyl group, interposed therebetween are wound up to thereby form a capacitor element. The content of binder in the separator is adjusted to 10-20% based on the total weight of separator before subjecting the capacitor element to restoration and chemical conversion. After the restoration and chemical conversion, the capacitor element is immersed in a liquid mixture prepared by mixing a polymerizable monomer, an oxidizer and a given solvent together so that polymerization reaction of conductive polymer is effected in the capacitor element to thereby form a solid electrolyte layer. The thus obtained capacitor element is inserted in a sheath case, and its opening end is fitted with sealing rubber. Sealing is accomplished by fastening operation, and aging is performed. Thus, a solid electrolytic capacitor is obtained.