Manganites with perovskite structure show peculiar properties such as colossal magnetoresistanece (CMR) effect and metal-to-insulator (MI) transition accompanying the charge and orbital ordering. In this study, magnetic domain structures in the CMR manganites; La_5/8-xPr_xCa_3/8MnO₃ ,(Nd_1-xSm_x)_1/2Sr_1/2MnO₃ and Nd_0.5Ca_0.5Mn_1-yCr_yO₃ were investigated by the low-temperature Lorentz electron microscopy. In La_5/8-xPr_xCa_3/8MnO₃ for x=0.375 it is found that two types of characteristic ferromagnetic (FM) domain structure appear below the MI transition temperature around 100K. One is a typical large-scaled FM domain structure and the other is a much smaller ( a few tens of nanometers) striped-like FM domain structure. In addition, the spatial distribution of the charge/orbital ordered (CO/OO) insulator state and the ferromagnetic (FM) metallic one in La_5/8-xPr_xCa_3/8MnO₃ for x=0.375 were clearly demonstrated. The coexisting states are crucial to understand the peculiar properties found in manganites.