機械翻訳システムが日本に於いて本格的に研究開発され始めて約20年弱の年月が経過した。しかし、機械翻訳には色々な問題点がある。 ここでは、機械翻訳の現状を概観し、品質向上にあたっての問題点、方法を検討する。Almost 20 years have passed since the first steps were taken in Japan toward serious R&D in machine translation (MT) systems. Over these two decades, translation software developers have come up against a vast range of problems. In this paper, I shall give an overview of the current state of machine translation, and examine the problems developers are facing in improving the quality of machine translations, and how they are tackling those problems.