Prophylactic or therapeutic agent for inflammatory bowel disease

A method of treating an inflammatory bowel disease, comprising systemically administering composite particles having miR-29a and/or miR-29b carried on a carbonate apatite particle to a patient in need of treatment of the inflammatory bowel disease, wherein the carbonate apatite particles have an average particle diameter of 400 nm to 3000 nm, wherein the miR-29a and/or miR-29b is internalized into cells of an inflammatory bowel disease lesion and into dendritic cells localizing on a mucosa of the lesion, wherein the inflammatory bowel disease is effectively improved by an action of the miR-29a and/or miR-29b uptake directly into the cells of the lesion and by an action of the dendritic cells that have taken up the miR-29a and/or miR-29b.