A crystalline .alpha.-D-glucosyl .alpha.-D-galactoside which has a melting point of 119 123.degree. C.; a saccharide composition comprising the same; a process for producing the same or the saccharide composition comprising the same, which comprises (i) crystallizing .alpha.-D-glucosyl .alpha.-D-galactoside from its solution and (ii) collecting the grown crystalline .alpha.-D-glucosyl .alpha.-D-galactoside; a method for converting amorphous .alpha.-D-glucosyl .alpha.-D-galactoside to crystalline .alpha.-D-glucosyl .alpha.-D-galactoside in the presence of moisture; and a composition comprising the crystalline .alpha.-D-glucosyl .alpha.-D-galactoside or the saccharide composition comprising the same.