This study standardized catch per unit effort(CPUE) of the Korean longline fishery, which has been used to assess the status of stock as an index of abundance, for bigeye and yellowfin tunas in the Indian Ocean. The Generalized Linear Model(GLM) was used to analyze the fishery data, which were catch in number and effort data collected each month from 1971 to 2007 by $5;{ imes};5$ degree of latitude and longitude. Explanatory variables for the GLM analysis were year, month, fishing area, number of hooks between floats(HBF), and environment factors. The HBF was divided into three classes while the area was divided into eight subareas. Although sea surface temperature(SST) and southern oscillation index(SOI) were considered as environmental factors, only SST was used to build a model based on statistical significance. Standardized CPUE for yellowfin tuna showed a declining trend, while nominal CPUE for the species showed an increasing trend.