An anode body for a capacitor formed by subjecting the sintered body which is obtained by sintering the molded body of tungsten powder to chemical conversion treatment, which anode body is doped with potassium in the amount of 0.003 to 0.3 mass %; a method of producing an anode body for a capacitor formed by subjecting the sintered body which is obtained by sintering the molded body of tungsten powder to chemical conversion treatment, including a process of doping the anode body with potassium in an amount of 0.003 to 0.3 mass %; and a solid electrolytic capacitor using the anode body.