The present invention provides a chemical conversion body that is obtained from a niobium granulated product being porous and having high binding strength, and enables production of an electrolytic capacitor and element having high electrostatic capacitance; and a production method thereof. The capacitor of the present invention comprises a chemical conversion body which has a dielectric layer on its surface and has a metal element other than niobium distributed therein so that the metal element surrounds niobium; and a cathode formed on the dielectric layer on the surface of the chemical conversion body. The chemical conversion body is obtained by obtaining a niobium granulated product by mixing niobium hydride and a compound containing a metal element other than niobium to prepare a mixture; and subjecting the mixture to heat treatment at a temperature higher than a diffusion starting temperature of the compound containing a metal element other than niobium; sintering the resultant; and subjecting the sinte
