To inexpensively produce soda ash for a glass raw material in an easier process by crushing trona ore and calcining under a specific condition.

Trona ore is crushed and calcined in an atmosphere containing oxygen at 500-800°C for ≥5min. Preferably, the trona ore is crushed to ≤5mm granular diameter. The crushed trona ore may be subjected to deferrization treatment before or after the calcination, as necessary. Then, the treated trona ore is calcined in an oxygen atmosphere such as an air, preferably in a fluidized state for 5-30min. Although the resultant soda ash contains more impurities SiO2, CaO, MgO, Al2O3, K2O and Fe2O3 than usual highly purified product, practical trouble is not generated because any organic material is eliminated by oxidation and the impurities are usable as glass raw materials.