The research problem is concerned with the relationship between internal and external validity. Generally it is said that there is an inverse relationship between internal and external validity. Criticizing the inverse relationship, I support that generally there is a direct relationship between internal and external validity. The research method is content analysis. The main materials are books and journal articles which are related with research method and research validity especially. First of all I bring out the problems which are incurred from the perspective of an inverse relationship. I make 2 arguments against the inverse relationship. That is, first there is no empirical data for the inverse relationship. Second, the inverse relationship comes from the background of clinical research which is very different with educational research. Also I make 2 arguments for the direct relationship. That is, first there are very similar threats to internal and external validity. So internal and external validity can be increased or decreased by controlling the same threats at the same time. Then I analyze 29 experimental papers from the 'Journal of Educational Technology' to find data which are related to the arguments. The main result of the study is, generally there is an direct relationship between internal and external validity rather than an inverse relationship. And one of the ways to improve the external validity is to have self measurement of external validity coefficient by the researcher.