The purpose of this study was to understand PCK to improve professionalism of teachers and derive implications about proper teachings methods. For achieving these research purposes, different PCK and teaching methods in class of three teachers(A, B, C) were compared and analyzed targeting division of decimals for 6th grade. For this study, criteria of PCK analysis of teachers was set, PCK questionnaires were produced and distributed, teachers had interviews, PCK of teachers were analyzed, division of decimals class for 6th grade was observed and analyzed, and PCK of teachers and their classes were compared. The implications deriving from comparative analyzing PCK and classes are as follows. First of all, there was a close relation between PCK and classes, leading to a need for efforts of increasing PCK of teachers in every field in order to realize effective classes. Secondly, self study and in-service training are needed to enhance PCK of teachers. Thirdly, more of expertises and materials have to be provided on the instruction manual for teachers.