The dependences of microscopic magnetic domain on film thickness in unidirectional and isotropic exchange-coupled NiO/NiFe bilayers were investigated by magnetic force microscopy to better understand for exchange biasing. As NiO thickness increases, microscopic domain structure of unidirectional biased film changed to smaller and more complicated domains. However, for isotropic-coupled film a new cross type domain appeared with out-of plane magnetization orientation. The density of the cross domain is proportional to exchange biasing fields and the fact that the domain was originated by the strongest exchange coupling region was confirmed from the dynamic domain configuration during a magnetization cycle.