CrYstal structure of LiNH4SO4 was refined in phase II (room temperature) and phase III (190K) by the use of X-ray diffraction intensity with including hydrogen atoms. The least-squares calculations converged with residual parameter R=0.0362 and 0.0378 for phases II and III, respectively. At room temperature, thermal parameters of hydrogen atoms are large and residual electron density is notable around ammonium ions. This may indicate a partial disorderness of the ammonium ions. In the monoclinic phase III, the calculation was performed with considering the effect of twin domains. In the refined superstructure, ammonium ions with hydrogen atoms are perfectly ordered. Hydrogen atoms link nitrogen and oxygen of sulphate ions.