The polymer Langmuir-Blodgett films containing a large porphyrin chromophore were prepared from a copolymer (pADA-Por) consisting of N-[(N＇-aminopropyl)pyridyltriphenylporphyrinate (Zn(II))]acrylamide (Por) and N-adamantylacrylamide (ADA). The spreading behavior of the copolymer on the water surface was investigated by the measurement of surface pressure (pi)-surface area (A) isotherm. The isotherm indicates that the pADA-Por copolymer forms a stable condensed monolayer with a steep rise in surface pressure and has a collapse pressure of 30 mN/m where a hydrogen bonding based on amide structure is working as a self-assembling factor. The monolayer can be transferred onto solid supports giving a typical Y-type LB film. A flat orientation of the porphyrin ring in the LB films was discussed from the absorption dichroism measurement.