The fluorescence probe technique was used to investigate the characteristics of an amino group-containing polymer chain grafted onto a polyethylene microfiltration (MF) membrane. The amino group-containing polymer chain labeled with a dansyl group that served as a fluorescence probe was grafted onto a polyethylene MF membrane by radiation-induced graft polymerization. The conformational changes of the grafted polymer chain (graft chain) in various solvents were monitored by considering that the steady-state fluorescence emission spectrum of the dansyl group was affected by the polarity of the solvent, the polyethylene, and the graft chain itself. The shift of the emission peak wavelength of graft chains with different lengths demonstrated that the graft chain containing amino groups stretched in water and methanol and shrank in dimethylformamide, acetone, and benzene. These results corresponded to changes in solvent permeability through the membrane pore to which the amino group-containing polymer chains were grafted.