Neutrinoless double beta decay experiment is the only realistic method to investigate the Majorana nature and the absolute mass scale of neutrinos. The DCBA (Drift Chamber Beta-ray Analyzer) experiment can separately detect electrons from other background particles in a uniform magnetic field. The kinetic energy of each electron is obtained from its momentum measurement. Therefore no energy calibration is required. The test prototype DCBA-T2 obtained the energy resolution of about 150 keV (FWHM) for 976 keV internal conversion electrons from 207Bi More improved prototype DCBA-T3 is now under construction. Its energy resolution is expected to be less than 100 keV (FWHM) according to the simulation study with Geant4. The future detector (temporarily called Magnetic Tracking Detector: MTD) enlarged from DCBA-T3 can investigate effective neutrino mass down to about 0.03 eV, if sufficient amount of 150Nd source is available.