An experiment using a wire simulating an electron beam was carried out in atmosphere to find organic particles (5‐&mgr;m thickness collected from an ion pump) trapped in a low electric field. It was found that these needlelike charged flakes stood upright at the bottom surface of the beam chamber without applied electric field. In spite of large adhesive action between the particle and the inner chamber surface in air, it was also found that the sample microparticles were trapped at the low electric field of 2525 V/m. Furthermore, the measured charge on the samples ranged from 1×10−13C to 3×10−13C. Our new theoretical analyses for the samples show that the electric field acting on the needlelike microparticles is enhanced approximately 104times from the results of the atmospheric experiment, and that the charged particles in vacuum can be trapped at a lower electric field of 70 V/m in the TRISTAN accumulation ring (time average electric field at the beam current of 30 mA) because of weak adhesion between the particles and an inner chamber surface rather than that in atmosphere. Therefore, microparticle trapping phenomena can be caused by such a charged particle coming from an ion pump or a distributed ion pump used in an electron accelerator.