This thesis aims at examining the way of science writing of 『Seonghosaseol』 and 『Uisanmundab』 in terms of rhetorical devices and considering what they hold for current sciece writing. The reason why I intend to take these two works as analysis object is related with the socio-cultural circumstances of 18th century in Joseon dynasty. 『Seonghosaseol』 was written before large inflow of western knowledge and information, otherwise 『Uisanmundab』 is written during this period. So by examining these two works we can compare and analyze what kind of academic development they achieve between traditional study and western science, and what kind of writing process they choose. First, in the case of 『Seonghosaseol』, it is a prototype of encyclopedic writing and at the same time it reflected the author’s opinion in the direct way and often expose his own experience. Although it included quite a mistake in scientific inferences, it also became a good reference for activities of the students under learning in that he put out bold inferences. Considering that those kind of bold inferences couldn’t be put out in 19th century, 『Seonghosaseol』 deserves high marks for putting out its own inference without being sunk by knowledge or information. in the case of 『Uisanmundab』, it put out more epoch-making, logical and elaborate inferences. Moreover it could make more persuasive and dense disputes by using narrative structure. Both 『Seonghosaseol』 and 『Uisanmundab』showed verbalizing in constructing of the statement. This is a diffrentiating feature from nominalizing which is considered as a standard expression in the modern science writing since Newton. Verbalizing in the expression shows the progress itself of acting and circumstance rather than its concept. 『Seonghosaseol』 and 『Uisanmundab』 suggest a possibility of an alternative on the problems which modern science writing shows such a rhetoric of objectification or delivery of fait accompli.