To obtain highly pure tin oxide having small alkali and chlorine contents.

This method for producing stannous oxide comprises producing stannous hydroxide by the neutralization reaction of the acidic aqueous solution of a stannite salt with an alkali aqueous solution and subsequently dehydrating the produced stannous hydroxide to produce the stannous oxide. Therein, the mixture solution of ammonia water with ammonium bicarbonate is used as a neutralization solution. The acidic aqueous solution of the stannite salt is reacted with the neutralization solution at a pH of 6.0-10 at a solution temperature of ≤50°C, and the produced stannous hydroxide precipitates are filtered off, washed with water and subsequently dehydrated to produce the stannous oxide. The obtained stannous oxide has an alkali content of ≤10 ppm and a chlorine content of ≤50 ppm and is easily soluble in acids.