The problem is to provide novel crystals of 5'-glucosyl adenosine the crystal structure of which has been elucidated, a 5'-glucosyl adenosine crystal-containing powder containing these crystals, the use of the same as a medical drug, and further, the use of the same as a cosmetic material or food product. The above-mentioned problem can be solved by providing crystals of 5'-glucosyl adenosine hydrochloride formed from one molecule of 5'-glucosyl adenosine and one molecule of hydrochloric acid.