The non-zero neutrino mass is an obvious fact beyond the Standard Model, but then the origin of the neutrino mass is still unknow. Determining the Dirac or Majorana nature of the massive neutrinos is a fundamentally important step toward Physics beyond the Standard Model, and it can be examined by neutrino-less double beta decay (0ν2β) search experiments. The experimental technique for the 0ν2β search falls roughly into two categories: calorimetry for 2β energy measurement and tracking for background suppression. It is a major challenge to acquire a high energy resolution and low backgrounds simultaneously.

In this talk, I propose a novel technique for the 0ν2β search, utilizing a time-of-flight both for 2β detection with a high energy resolution and efficient background suppression. Although this technique is still under investigation, I will show a preliminary sensitivity for 0ν2β expected from a Monte Carlo simulation study.