Eye-tracking approach allows us to collect and analyze data for a wide range of measures of eye-movements, to relate these to language processing, and to have insight of language processing (Conklin, Pellicer-Sánchez, and Carrol, 2018). The current study aims to investigate how ESL university students process the sentences with complex noun phrases modified by relative clauses. Two types of sentences with complex noun phrases were examined: complex noun phrases modified by relative clauses located in a sentence subject (syntactic-based processing) and those located in a sentence object (semantic-based processing). In total, 32 EFL university students participated in this study. Fixation count, regression rate, first reading time, and total reading time of areas of interest were examined. The eye-tracking results showed that the participants showed significantly higher regression rates on noun 2 than noun 1 in both types of complex noun phrases. In terms of verb selection, however, the results showed contrasting aspects : noun 1(verb 1 selection) preference in syntactic-based processing whereas noun 2(verb 2 selection) preference in semantic-based processing,