Atomic force microscopy was applied to investigate the microscopic molecular structures of polyimide Langmuir-Blodgett (LB) films. The polyimide chains of a monolayer film on graphite were observed. It was found that the polyimide LB film with a groovy surface occurs due to the orientation of polyimide chains. By horizontal deposition the polyimide chains show a zigzag structure, while by vertical deposition the polyimide chains show a straight-line structure. Moreover, the polyimide chains are always oriented along the direction of deposition. It is suggested that the polyimide chains are oriented by the LB technique.