A method of producing a garnet-type solid electrolyte suitable for use in a lithium battery wherein the electrolyte is represented by a composition formula Li7La3Zr2O12 and has (110) face, (1-10) face, (112) face, (1-12) face, and (11-2) face as a crystal face, the method comprising:
- a preparation step of preparing a lithium-containing compound, a lanthanum-containing compound, and a zirconium-containing compound;
- a mixing step of obtaining a mixture by mixing the lithium-containing compound, lanthanum-containing compound, and zirconium-containing compound such that a molar ratio among the elements satisfies Li:La:Zr=a:b:c, where a is from 120 to 160, b is from 1 to 5, and c is from 1 to 5;
- and
- a heating step of heating the mixture at from 400 to 1,200° C.