Tachibana et al, have developed the series of the charge-transfer complexes (APT materials) of azobenzene-containing alkyl chain pyridiniums and TCNQ, which exhibits marked conductivity change upon the photoisomerization of the azobenzene group, providing a new class of ultrathin organized molecular films. The in situ measurements performed on the APT(8-12) and APT(12-12) films have detected the clear ESR spectral change upon the photoisomerization, indicating the modification of the TCNQ columnar structures. The observed changes in the magnetic parameters are discussed in relation to the possible mechanism of the conductivity change.