The initial phase of the SHE-Mass project -- precision mass measurements of superheavy nuclei with a multi-reflection time-of-flight mass spectrograph (MRTOF-MS) coupled with the gas-filled recoil ion separator GARIS-II -- has successfully been carried out. In a series of the experiments, masses of a wide variety of heavy/superheavy nuclei have been measured [1,2,3]. In particular, masses of mendelevium ($Z=101$) isotopes in the vicinity of the $N=152$ deformed neutron shell closure have been directly measured for the first time . For the project, dedicated experimental devices to produce low-energy ion beams such as a cryogenic gas catcher and ion traps and sophisticated measurement scheme for the MRTOF-MS have also been developed. The details for the measurements and developments will be presented.
 P. Schury et al., Phys. Rev. C 95 (2017) 011305
 M. Rosenbusch et al., Phys. Rev. C (submitted)
 Y. Ito et al., Phys. Rev. Lett. (accepted)