The influence of the defects introduced into the diamond film by nitrogen doping, on an electron emission has been studied by the electron spin resonance (ESR) method. It was observed that a large amount of nitrogen doping (N/C = 1 similar to 10) caused the crystal quality to deteriorate through the introduction of a paramagnetic defect into the diamond film. The current density of the electron emission was increased to 250 muA/cm(2) with an increase of defect density within the diamond film.