A solid electrolytic capacitor comprising: an anode of valve metals or alloy of which main component is valve metals; a dielectric layer formed by anodizing the anode; and a cathode formed on the dielectric layer, wherein the dielectric layer comprises a first dielectric layer located on the anode side and a second dielectric layer formed on the first dielectric layer, and oxygen concentration of the second dielectric layer is decreased from the first dielectric layer side toward the cathode side.