Regarding a composite particle in the related art, an antibody and a dye are bound to the surface of the particle. Therefore, it is not possible to bind both the antibody and the dye high in number. Accordingly, the present invention provides a composite particle, wherein a large acoustic wave can be emitted and both the antibody and the dye can be bound high in number. A composite particle including a core particle, a dye bound to the above described core particle, and an antibody, wherein the above described antibody is bound to the above described dye, is suitable for use.