Upekhā is introduced as one of the major qualities of Buddhist practice. It has the meaning of a neutral feeling, observation without subjective conception, and wisdom free of discrimination; however, it is mainly understood as a neutral attitude of the mind which means an inner harmony or balancing quality. The background of this understanding originates in the Visuddhimagga 淸淨道論, published in the fifth century by Buddhagosa. Buddhagosa classfied Upekhā mentioned in the Pāli nikāya by 10 kinds according to its function such as neutrality, attachment, and observation. Most conceptual understanding and academic discussion of Upekhā since then has been based on this way of classification - through Buddhist Abhidhamma scriptures in the later 5th century, beginning with Visuddhimagga, to modern literature. But when the Pālī nikāya is reviewed in detail, there exist more varied and flexible meanings of Upekhā than are categorized in Visuddhimagga. These various detailed classifications include discernment, calmness, pure consciousness, ignorance, satisfaction and detachment. Realizing these issues, I point out a limitation of the existing understanding of Upekhā based on Visuddhimagga, and at the same time show its various uses in the Pāli nikāya. I first examine the use of Upekhā as found in Pāli-nikāya, and then classified them according to their function and characteristic. Second, I investigate the 10 kinds of functional classifications as found in Visuddhimagga. Finally, I examine the problems of classifications of Upekhā in Visuddhimagga based on its use in Pāli nikāya. When we only rely on the expressions of Upekhā in Visuddhimagga and exclude those found in the nikāya, the horizon of conceptual understanding about Upekhā may be narrowed. Furthermore, there is the potential that the various meanings may become distorted or miscommunicated. Therefore, there is a need for a more delicate approach towards the term of Upekhā.