In practices and academics, the growth/decline of a brand or product sales is often measured with market shares. However, this method does not really gain insight into loyalty and perception of consumers toward brands and products. Therefore, it is significant to come up with a research into the “market share of the minds” of consumers, in contrast to the concept of market shares. None of the previous literature regarding market shares and Mind Shares has proposed any substantial theoretic researches or quantified. This paper starts with the concept of “Mind Shares” by Keegan (2002) and combines two variables, such as confidence and resistance, as the main contents of loyalty, to establish a new theoretic foundation and develop the calculation method for the quantification of the concept of Mind Shares. This study attempted to validate the Mind Shares in the mobile service providers market, and surveyed mobile phone users. The data from questionnaire survey showed that confidence and resistance are both positively correlated with loyalty, and these two variables are capable of predictability on loyalty. It is considered that this paper lays down the theoretic foundation of Mind Shares and contributes applications.