PROBLEM TO BE SOLVED: To provide a probe for dual imaging having high magnetic resonance relaxation ability as well as high optoacoustic signal generation ability, thereby usable to both magnetic resonance imaging and optoacoustic imaging and a method for producing a composite particle to be used thereto.SOLUTION: A probe for dual imaging to be used for magnetic resonance imaging and optoacoustic imaging contains a composite particle in which a hydrophilic coat is formed on the surface of a manganese (II) oxide-containing particle. The production method of the composite particle to be used for the probe for dual imaging is characterized by forming a hydrophilic coat by coating an amphiphilic high molecular compound on the surface of a manganese (II) oxide-containing particle.
