PURPOSE: To provide a calcium absorption-accelerating agent further having an intestinal disorder-preventing activity by compounding a galacto oligo saccharide having a calcium intestinal absorption-improving activity as an active ingredient.

CONSTITUTION: A calcium absorption-accelerating agent contains a galacto oligo saccharide, preferably o-β-D-galactopyranosyl-(1→4)-o-β-D- galactopyranosyl-(1→4)-D-glucose of the formula as an active ingredient. The galacto oligo saccharide, preferably 4'-galactosyl lactose, can be effectively prepared from lactose or a material containing the lactose by the use of β- galactosidase obtained from Criptococcus.laurentii.variety.laurentii (FERM P-7629). The galactosidase is stable against heat and acids, and thereby extremely useful for applications to such as foods and feeds.