An object of the invention is to provide a transdermal absorption preparation capable of sustaining the blood morphine concentration at an effective level over at least 48 hours, etc. This transdermal absorption preparation comprises a medicinal composition for transdermal absorption in which an active ingredient selected from morphine and salts thereof is blended in such an amount as corresponding to the saturation solubility or more in an active ingredient-holding vehicle having fluidity at a temperature around the human skin surface temperature and at least a portion of the active ingredient is held in a crystalline form, characterized in that, in the case where a preparation obtained from the above-described medicinal composition for transdermal absorption is applied to the uninjured skin of the back of a white rabbit having been shaven with electrical clippers for 72 hours, the available amount of the active ingredient per single dose of the preparation is from 10 mg to 400 mg in terms of morphine base, and the plasma concentrations of the active ingredient 24 hours and 48 hours after the application of the preparation under the above-described conditions are each at least 40 ng/mL in terms of morphine base, and so on.