PURPOSE: To obtain highly crystalline stannosilicate which has excellent ion exchangeability, etc., and is useful as a catalyst, sorbent, etc. by bringing a water-soluble tin salt, silica source, group IA or group IIA metal hydroxide or amine into reaction with each other in an aq. medium.

CONSTITUTION: The water-soluble tin salt (e.g.; stannous chloride), the silica source (e.g.; colloidal silica) and the group IA or group IIA metal hydroxide in periodic table (e.g.; sodium hydroxide) or the amine e.g.; triethanol amine are brought into reaction with each other in the aq. medium. The formed crystalline stannosilicate is then recovered, by which the highly crystalline stannosilicate expressed by the formula (M is group IA metal, group IIA metal, quaternary amine; (x) is 1.5 to 4; (y) is 4 to 15; R is amine; (z) is 0 to 4) is obtd. The resulted highly crystalline stannosilicate is adequately used as the sorbent, etc., for separating hydrogen sulfide from gaseous flow contg. for example, hydrogen and hydrogen sulfide.