A solid-state electrolytic capacitor includes: a planar anode terminal having a first plane connected to an anode of a capacitor element and a second plane arranged opposite to the first plane; a planar cathode terminal having a first plane connected to a cathode layer of the capacitor element and a second plane arranged opposite to the first plane and in the same plane of the second plane of theanode terminal; an insulating external package resin for covering the capacitor element, the anode terminal, and the cathode terminal while exposing the second plane of the anode terminal and the second plane of the cathode terminal. The anode terminal includes a first thick portion having a part of the first plane of the anode terminal and the second plane of the anode terminal and a first thin portion having a part of the first plane of the anode terminal, connected to the first thick portion, and thinner than the first thick portion. The cathode terminal includes a second thick portion having a part of the first plane of the cathode terminal and the second plane of the cathode terminal and a second thin portion having a part of the first plane of the cathode terminal, connected to the second thick portion, and thinner than the second thick portion. This solid-state electrolytic capacitor can reduce the equivalent series inductance and can be mounted stably on an object.