A method (100) for producing a solid electrolyte for an all-solid state battery, the solid electrolyte having the following chemical formula XM2(PS4)3, where P is phosphorus, S is sulfur and X is lithium (Li), sodium (Na), silver (Ag) or magnesium (Mg0,s) and M is titanium (Ti), zirconium (Zr), germanium (Ge), silicon (Si), tin (Sn) or a mixture of X and aluminium (X + Al) and the method including: mixing powders so as to obtain a powder mixture; pressing a component with the powder mixture; and sintering the component for a period of time equal to or greater than 100 hours so as to obtain the solid electrolyte (16). The solid electrolyte exhibits the peaks in positions of 2Θ = 13,64° (±1°), 13,76° (±1°), 14,72° (±1°), 15,36° (±1°), 15,90° (±1°), 16,48° (±1°), 17,42° (±1°), 17,56° (±1°), 18,58° (±1°), and 22,18° (±1°) in a X-ray diffraction measurement using CuKα line, where IA is the intensity in arbitrary units of the peak at 13,64°(±1°) and IB is the intensity in arbitrary units of a peak at 23,34° (±1°), (IA - IB)/(IA + IB) > 0. (±1°), (IA - IB)/(IA + IB) > 0. The disclosure is also related to a method of producing a solid electrolyte.