This study aimed to determine how elementary mathematics currently deals with external ratio, the ratio between two different types of magnitude, and to find ways to address it in textbooks. By examining the definition of ratios and the handling of external ratios in the elementary school mathematics curriculum and textbooks, it was found that the method of dealing with external ratios varies based on the curriculum period and is inconsistent. The suggestions derived for dealing with external ratios in elementary mathematics are as follows. First, the context of internal and external ratios needs to be explained. Second, when dealing with external ratios, the aspect of the ratio and the aspect of the third quantity should be addressed. Finally, the definition of the ratio currently presented in the context of the internal ratio should be established to encompass the external ratio.