The present invention provides a carbon monoxide removal agent that can be easily administered to a patient by injection or orally. The carbon monoxide removal agent of the present invention contains, as an active ingredient, an inclusion complex in which a cyclodextrin dimer represented by chemical formula (1) below includes a water-soluble metalloporphyrin. (In the formula, m represents either of number 1 or 2 and n represents any of number 1, 2, or 3.)
