Searching for the electron electric dipole moment (eEDM) is a powerful probe for CP violation in physics beyond the Standard Model. The most stringent upper limit on the eEDM |de| < 1.1 × 10−29 e·cm was given by the ACME II experiment (Nature, 562 (2018) 355-360), by measuring electron spin precession in polar molecules, thorium monoxide. Now we are constructing the third generation of the experiment to improve the sensitivity by an order of magnitude. Many parts of our apparatus will be upgraded to improve statistical sensitivity, such as a cryogenic buffer gas beam source, electro- static molecular lens, and fluorescence photodetectors. We are also preparing new laser optics, a field plate system, and a magnetic shielding system for suppressing systematic errors. In this talk, I will introduce an overview of the experiment and present our recent progress towards a new result.