The complex crystal of the present disclosure is a complex crystal having a structure in which supramolecular units each composed of two or more types of molecules are arrayed. Each of the supramolecular units contains a cyanoacrylic acid derivative and a trisubstituted methylamine as the molecules. The complex crystal has, between the supramolecular units, molecular cavities in each of which a guest molecule for which the supramolecular unit is a host is not disposed. The complex crystal of the present disclosure can have a property of incorporating a chemical substance therein and can exhibit a great change in a characteristic when incorporating the chemical substance therein.