The purposes of this research were to study misconceptions in educational research and to determine graduate students reasons that led to the misconceptual responses. The population of the study was 206 graduate students at the Faculty of Education, Chiang Mai University who took the educational research course in academic year 1995 and an additional 9 research and statistics in education program graduate students, code40. The study tool was a diagnostic test that combined true/false questions with multiple choices. Frequency, percentage, and content analysis were used and presented in the descriptive manner. The findings were as follows: Graduate Students have the 3 most common misconceptions regarding educational research which were: (1) They confused external validity with internal validity and translated the meaning of external to internal validity by position from into or out of something. (2) Concerning the delimitation of population, students misunderstood that it should be written in the form of definition and selection of population, and also responded that purpose of the thesis proposal was dealing with the presentation of the thesis. And (3) the confusion of deductive method and inductive method. Having with 7 misconceptions were high, while those having only 2 misconceptions were low. One misconception was the lowest, that good research is experimental research and quality of research determines by using advanced statistical method to analyze the data.