The disclosure relates to an all-solid-state capacitor which has a high capacitance, is excellent in frequency characteristics, and can be made compact. An all-solid-state capacitor of the disclosure includes an inorganic solid electrolyte, and a pair of current collectors disposed so as to hold the inorganic solid electrolyte in between, the inorganic solid electrolyte having a main crystal phase of perovskite crystal structure that is expressed by a general formula, ABO3. A-site elements include two different elements, namely Li and M which is at least one of elements in Group 2 of the Periodic Table of Elements, and B-site elements include two different elements, namely Ti and M′ which is at least one of elements in Group 5 of the Periodic Table of Elements.