In this study, the liquid-vapor (L-V) separator equipped with liquid-level meter is developed. In the developed L-V separator, the flange is designed to be attachable so that the separator can be flexibly applied under any cases where the volumetric of L-V separator is varied by the system requirement. The leak-tightness between the attachable flange and the chamber is experimentally confirmed with the use of double groove indium wire sealing even under the high pressure up to 20 bar. In addition, the liquid-level meter is designed and fabricated to figure out the inner state of L-V separator. It consists with 19 carbon composition resistors in series. All resistors are separately calibrated in the temperature range from 77 K to 200 K. The performance of the L-V separator and the liquid-level meter is investigated with experimental tests, and the result is presented in this paper.