In this paper, mass measurement devices (MMDs) developing by the authors for use in the International Space Station (ISS) are reviewed. First, Space Balance, which is a small mass measurement device (SMMD), is reviewed. In Space Balance, the momentum conservation between two objects, the subject mass and the reference mass, are compared. Then Space Scale, which is a body mass measurement device (BMMD), is reviewed. In Space Scale, a human subject is pulled using rubber string. Force is measured using a force transducer and acceleration is measured using optical interferometer. Both Space Balance and Space Scale have shown high accuracies in the ground experiments.