The purpose of this study was to examine the impact of choice of income definition and equivalence scale on inequality measures using 1979-2005 household survey data conducted by the Directorate-General of Budget, Accounting and Statistics. Main results and suggestion are as follows: 1. Different definition of disposable income have a significant impact on inequality index and inequality distribution. Since covering comprehensively income subject that will affect household well-beings, Luxembourg disposable income is a better proxy to measure economic well-being. 2. Because the household structure of Taiwan have undergone rapid changes for past thirty years, when measuring long-term household economic well-beings, one should apply equivalence scale adjusting for household size and composition, and better use normative inequality measures to present long-run inequality tendency.