Provided are a slurry for a solid electrolyte, which can reduce the usage of a polymer binder, a method for producing a solid electrolyte layer, and a method for producing an all-solid-state battery. Disclosed is a slurry for a solid electrolyte, the slurry comprising a solvent, a lithium compound, and crystal particles of a garnet-type ion-conducting oxide represented by a general formula (Lix−3y−z,Ey,Hz)LαMβOγ (where E is at least one kind of element selected from the group consisting of Al, Ga, Fe and Si; L is at least one kind of element selected from an alkaline-earth metal and a lanthanoid element; M is at least one kind of element selected from a transition element that can be six-coordinated with oxygen and typical elements in groups 12 to 15 of the periodic table; 3≤x−3y−z≤7; 0≤y≤0.25; 0