>Molecular thin films fabricated using novel organic materials such as dendrimer with a dye, rhodamine B(Rh-B), core was investigated by a pump-probe measurement for a ultrafast time-resolved spectroscopy with a time resolution of approximately 160 fs. The photon energy transfer caused by the interaction of the dendrimer molecules, has been measured in a term of absorbance. The wavelength of the pump light was 550 nm and a white continuum light spanning from 450 nm to 750 nm was used as a probe light. A spin-coated molecular film made of the Rh-B cored dendrimer (molecular weight was 4,885) has a relatively high molecular-number density of 1.27x10¹⁶ (mol/cm³). A strong stimulated emission at a wavelength 612 nm was measured, whose fast decay was assumed to be caused by intermolecular actions between the Rh-B cored molecules. The lifetime of the excited state was measured to be as small as 10 ps. Several types of molecular films with different molecular densities were compared, and also discussed in the cases with different pump energy.