To obtain a medicinal composition comprising an effective ingredient selected from the group consisting of omeprazole and a physiologically acceptable salt thereof as an active ingredient, having excellent preservation stability and achieving rapid elution of the effective ingredient in the environment at pH≥5, preferably pH≥6.

A core part is protected from an enteric film by forming an interlayer provided between the core part containing the effective ingredient and the enteric film as a substantially water-insoluble and water-permeable layer using a water-insoluble polymer. Water permeated through the interlayer is absorbed on the core part by formulating a substance swelling by absorbing the water in the core part. Cracks and/or cleavages are then rapidly produced in the interlayer by swelling of the core part. As a result, the effective ingredient can be eluted from the core part at an ultrahigh rate.