This study is to examine and classify the phasic characteristics of organic thoughts in modern architecture. Organic architects have applied organic thoughts to solutions for the problems of each period in architecture since modern times. As results of this study, the architecture of organic thoughts from 1850s to 1940s could be divided into two phases. The phasic characteristics of the first phase from 1850s to 1910s was physical resemblance in real or fantastic appearance that the work of art and architecture should imitate organic forms from the view of solid empiricism. The phasic characteristics of the second phase from 1920s to 1940s was organic growth that the form appropriate to a work of art and architecture should grow from the nature of the problem itself as a system in nature grows from the view of pragmatism and was organic unity that the form and function or the form and content of a work of art should be inseparably integrated as the form in nature should grow out of the inner nature of the thing and be an expression of that inner nature from the view of expressive theory.