One aspect of the present invention provides a sulfide solid-state battery provided with: a negative electrode collector containing copper; a negative electrode mix layer disposed on the negative electrode collector, and containing a negative electrode active material; a positive electrode mix layer containing a positive electrode active material; a sulfide solid electrolyte layer sandwiched between the negative electrode mix layer and the positive electrode mix layer, and having a protruding portion that protrudes from a peripheral edge of the negative electrode mix layer and extends up to the negative electrode collector; and a reference electrode disposed in the protruding portion.