This study measures and compare efficiency of the eight Korean IT sectors. Data envelopment analysis (DEA) is employed to measure efficiency of about 900 firms with annual sales over 10 billions won in the following eight sectors: telecommunication service, wireless communication service, digital contents, broadcasting service, wireless communication device, semiconductor, display panel, and computer-related service. DEA is a linear programming model for measuring the relative efficiency of decision making units (DMUs) with multiple inputs and outputs. Total number of employees, amount of investment, and cost of sales are considered as inputs, and output variables include value added, net income, and sales. Every firm in every sector is evaluated together by DEA, and then, Kruskal-Wallis test is run to compare the efficiency of the sectors. It is found that wireless communication service and telecommunication service have relatively high efficiency while digital contents, wireless communication device, and semiconductor show low performance. The results of efficiency evaluation and benchmarking way for improving efficiency obtained from this study are expected to provide fruitful implications for IT policy making.