A fluorescent two-dimensional network patterning was fabricated with polymer LB films. An amphiphilic polymer consisting of N-dodecylacrylamide, N-11-acryloylundecyl-4-vinylpyridinium salt and 1-pyrenylacrylamide forms a stable monolayer, which is transferred onto solid substrates yielding LB films. The absorption and emission spectra of the LB films indicate that pyrene chromophore exists in the LB film. On irradiation, photo-crosslinking reaction of the acryloyl group, which is aligned on each interlayer hydrophobic tail surface of LB films occurs efficiently. Consequently, the irradiated polymer LB film becomes insoluble in organic solvents due to the formation of the two-dimensional polymer network in the LB film. The patterned fluorescent polymer LB film was confirmed by the fluorescence microscopy.