A solid electrolyte (10) of the present disclosure includes: a porous dielectric (11) having a plurality of pores (12) interconnected mutually; an electrolyte (13) including a metal salt and at least one selected from the group consisting of an ionic compound and a bipolar compound, the electrolyte (13) at least partially filling an interior of each of the plurality of pores (12); and a surface adsorption layer (15) adsorbed on inner surfaces of the plurality of pores (12) to induce polarization. The surface adsorption layer (15) may include water adsorbed on the inner surfaces of the plurality of pores (12). The surface adsorption layer (15) may include a polyether adsorbed on the inner surfaces of the plurality of pores (12).