A process for producing a particulate composition comprising anhydrous crystalline 2-O-a-D-glucosyl-L-ascorbic acid, said process comprising the following steps (a) to (e): (a) allowing a cyclomaltodextrin glucanotransferase to act on a solution comprising either liquefied starch or dextrin and L-ascorbic acid as materials, and then allowing a glucoamylase to act on the resulting solution to obtain a solution comprising 2-O-α-D-glucosyl-L-ascorbic acid in a 2-O-α-D-glucosyl-L-ascorbic acid production yield of at least 27% by weight; (b) purifying the resulting solution comprising 2-O-α-D-glucosyl-L-ascorbic acid to give a 2-O-α-D-glucosyl-L-ascorbic acid content of over 86% by weight, on a dry solid basis; (c) precipitating anhydrous crystalline 2-O-α-D-glucosyl-L-ascorbic acid from the purified solution with a 2-O-α-D-glucosyl-L-ascorbic acid content of over 86% by weight, on a dry solid basis, by a controlled cooling method or a pseudo-controlled cooling method; (d) collecting the precipitated anhydrous crystalline 2-O-α-D-glucosyl-L-ascorbic acid; and (e) ageing, drying, and optionally pulverizing the collected anhydrous crystalline 2-O-α-D-glucosyl-L-ascorbic acid without dissolving and recrystallizing it to obtain a particulate composition comprising anhydrous crystalline 2-O-α-D-glucosyl-L-ascorbic acid which comprises 2-O-α-D-glucosyl-L-ascorbic acid in a content of, on a dry solid basis, over 98.0% by weight but below 99. 9% by weight, and has a degree of crystallinity for anhydrous crystalline 2-O-α-D-glucosyl-L-ascorbic acid of at least 90%, when calculated based on the powder X-ray diffraction profile of the particulate composition; wherein the controlled cooling method is a cooling method wherein the temperature T of the solution at time t is expressed by the formula: T = T o − T o − T f t / τ 3 wherein τ is the operation time established for the crystallization step, T o is the temperature of the solution at the initiation of crystallization, and T f is the targeted liquid temperature at the termination of crystallization; and wherein the pseudo-controlled cooling method is a cooling method wherein the liquid temperature T is allowed to decrease linearly or stepwisely with time t such that (T 0 -T m) is at least 5 % but less than 50 % of the total temperature change (T 0 -T f), wherein T m is the liquid temperature at time t=τ/2. (a) allowing a cyclomaltodextrin glucanotransferase to act on a solution comprising either liquefied starch or dextrin and L-ascorbic acid as materials, and then allowing a glucoamylase to act on the resulting solution to obtain a solution comprising 2-O-α-D-glucosyl-L-ascorbic acid in a 2-O-α-D-glucosyl-L-ascorbic acid production yield of at least 27% by weight; (b) purifying the resulting solution comprising 2-O-α-D-glucosyl-L-ascorbic acid to give a 2-O-α-D-glucosyl-L-ascorbic acid content of over 86% by weight, on a dry solid basis; (c) precipitating anhydrous crystalline 2-O-α-D-glucosyl-L-ascorbic acid from the purified solution with a 2-O-α-D-glucosyl-L-ascorbic acid content of over 86% by weight, on a dry solid basis, by a controlled cooling method or a pseudo-controlled cooling method; (d) collecting the precipitated anhydrous crystalline 2-O-α-D-glucosyl-L-ascorbic acid; and (e) ageing, drying, and optionally pulverizing the collected anhydrous crystalline 2-O-α-D-glucosyl-L-ascorbic acid without dissolving and recrystallizing it to obtain a particulate composition comprising anhydrous crystalline 2-O-α-D-glucosyl-L-ascorbic acid which comprises 2-O-α-D-glucosyl-L-ascorbic acid in a content of, on a dry solid basis, over 98.0% by weight but below 99. 9% by weight, and has a degree of crystallinity for anhydrous crystalline 2-O-α-D-glucosyl-L-ascorbic acid of at least 90%, when calculated based on the powder X-ray diffraction profile of the particulate composition; wherein the controlled cooling method is a cooling method wherein the temperature T of the solution at time t is expressed by the formula: T = T o − T o − T f t / τ 3 wherein τ is the operation time established for the crystallization step, T o is the temperature of the solution at the initiation of crystallization, and T f is the targeted liquid temperature at the termination of crystallization; and wherein the pseudo-controlled cooling method is a cooling method wherein the liquid temperature T is allowed to decrease linearly or stepwisely with time t such that (T 0 -T m) is at least 5 % but less than 50 % of the total temperature change (T 0 -T f), wherein T m is the liquid temperature at time t=τ/2. wherein τ is the operation time established for the crystallization step, T o is the temperature of the solution at the initiation of crystallization, and T f is the targeted liquid temperature at the termination of crystallization; and wherein the pseudo-controlled cooling method is a cooling method wherein the liquid temperature T is allowed to decrease linearly or stepwisely with time t such that (T 0 -T m) is at least 5 % but less than 50 % of the total temperature change (T 0 -T f), wherein T m is the liquid temperature at time t=τ/2.